document_title: Tomb of the Unknown Soldier (Arlington)

question_text: who patrols the tomb of the unknown soldier

text: Tomb of the Unknown Soldier (Arlington)

text: Tomb of 1921[edit]

text: On March 4, 1921, the United States Congress approved the burial of an unidentified American serviceman from World War I in the plaza of the new Memorial Amphitheater. On November 11, 1921, the unknown soldier brought back from France was interred below a three-level marble tomb. The bottom two levels are six marble sections each and the top at least nine blocks with a rectangular opening in the center of each level through which the unknown remains were placed through the tomb and into the ground below. A stone, rather than marble, slab covers the rectangular opening.[4][5][6]

text: Tomb of 1931[edit]

text: Since 1921 the intent was to place a superstructure on top of the Tomb, but it was not until July 3, 1926, that Congress authorized the completion of the Tomb and the expenditure of $50,000 (with a completed cost of $48,000). A design competition was held and won by architect Lorimer Rich[nb 1] and sculptor Thomas Hudson Jones. An appropriation from Congress for the work was secured and on December 21, 1929, a contract for completion of the Tomb itself was entered into. The Tomb would consist of seven pieces of marble in four levels (cap, die, base and sub-base) of which the die is the largest block with the sculpting on all four sides.[4][7]

text: Quarrying the Yule marble (3.9 miles south of Marble, Colorado by the Vermont Marble Company) was a one-year process beginning in 1930. The cap was quarried on the first attempt but the base required three tries. The large middle block also required three tries. In late January 1931, the 56 ton middle block was lifted out of the quarry. The quarrying involved 75 men. When the block was separated from the mountain inside the quarry it weighed 124 tons. A wire saw was then brought into the quarry to cut the block down to 56 tons.

text: On February 3, the block reached the marble mill site (in the town of Marble) after a four-day trip from the quarry. Here it was crated, then shipped to Vermont on February 8. The block was sawn to final size in West Rutland, Vermont, and fabricated by craftsmen in Proctor, Vermont, before it was shipped by train to Arlington National Cemetery, Virginia.[8] By September, all 7 blocks were on the grounds of the Tomb site, at Arlington.

text: Assembly began in September 1931. An imperfection was found in the base, requiring three more quarryings. By the end of December 1931, the assembly was completed. Finishing work followed with the carvings on the die block by the Piccirilli Brothers under the direction of the sculptor Thomas Jones.[4][9] (The brothers also carved the Lincoln statue for the Lincoln Memorial). The Tomb was completed without formal ceremony on April 9, 1932.[10]

text: The Tomb[nb 2] was placed at the head of the grave of the World War I Unknown. West of this grave are the crypts of Unknowns from World War II (south) and Korea (north). Between the two lies a crypt that once contained an Unknown from Vietnam (middle). His remains were positively identified in 1998 through DNA testing as First Lieutenant Michael Blassie, United States Air Force and were removed. Those three graves are marked with white marble slabs flush with the plaza.

text: The Tomb has a flat-faced form and is relieved at the corners and along the sides by neo-classical pilasters set into the surface with objects and inscription carved into the sides. The 1931 symbolism[9] of the objects on the north, south and east sides changed over time.[4][7]

text:
Tomb Dimensions[nb 3]
as of 2004[11] (xxx)* 1931 die block dimension coming out of the quarry.[8]

text:
Level
Length
Width
Height
Cubic Feet
Tons

Cap
12'-5.4"
6'-6.7"
1'-3.3"
100.69
8.56

Die
12'-3.0" (14'-0")*
6'-6.4" (7'-4.8")*
5'-2.1" (6"-0")*
385.43 (621.6)*
32.76 (52.84)*

Base
13'-10.0"
7'-11.9"
1'-11.1"
198.64
16.88

Sub-Base
14'-10.4"
9'-0.2"
1'-10.9"
255.81
21.74

text: The Unknown of World War I[edit]

text: On Memorial Day, 1921, four unknown servicemen were exhumed from four World War I American cemeteries in France, Aisne-Maine, Meuse-Argonne, Somme, and St. Mihiel. U.S. Army Sgt. Edward F. Younger, who was wounded in combat, highly decorated for valor and received the Distinguished Service Cross in "The Great War" selected the Unknown of World War I from four identical caskets at the city hall in Châlons-en-Champagne, France, on October 24, 1921.[6] Younger selected the World War I Unknown by placing a spray of white roses on one of the caskets. He chose the third casket from the left. The chosen Unknown was transported to the United States aboard the USS Olympia. Those remaining were interred in the Meuse Argonne Cemetery, France.[6]

text: The World War I Unknown lay in state in the Capitol Rotunda from his arrival in the United States until Armistice Day, 1921. On November 11, 1921, President Warren G. Harding officiated at the interment ceremonies at the Memorial Amphitheater at Arlington National Cemetery. During the ceremony, the World War I Unknown was awarded the Victoria Cross by Admiral of the Fleet Lord Beatty, on behalf of King George V of the United Kingdom.[12] (The United Kingdom Victoria Cross was placed with the soldier. Earlier, on March 4, 1921, the British Unknown Warrior was conferred the U.S. Medal of Honor by General of the Armies John Pershing.) In 1928, the Unknown Soldier was presented the Silver Buffalo Award for distinguished service to America's youth by the Boy Scouts of America.[13]

text: The Unknowns of World War II and Korea[edit]

text: On August 3, 1956, President Dwight D. Eisenhower signed a bill to select and pay the tribute to the Unknowns of World War II and the Korean War.[14] The selection ceremonies and the interment of these Unknowns took place in 1958. The World War II Unknown was selected from remains exhumed from cemeteries in Europe, Africa, Hawaii, and the Philippines.[15]

text: Two Unknowns from World War II, one from the European Theater and one from the Pacific Theater, were placed in identical caskets and taken aboard the USS Canberra, a guided-missile cruiser resting off the Virginia Capes. Navy Hospital Corpsman 1st Class William R. Charette, then the U.S. Navy's only active-duty Medal of Honor recipient who was an enlisted man, selected the World War II Unknown. The remaining casket received a solemn burial at sea.[15]

text: Four unknown Americans who died in the Korean War were disinterred from the National Cemetery of the Pacific in Hawaii. Army Master Sergeant Ned Lyle made the final selection.[15]

text: Both caskets arrived in Washington on May 28, 1958, where they lay in the Capitol Rotunda until the morning of May 30, when they were carried on caissons to Arlington National Cemetery. President Eisenhower awarded each the Medal of Honor, and the Unknowns of World War II and the Korean War were interred in the plaza beside their World War I comrade.[15]

text: The Unknown of Vietnam[edit]

text: This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (November 2017) (Learn how and when to remove this template message)

text: The designation of the Vietnam Unknown proved to be difficult – with improvements in DNA testing it is possible, though unlikely, that the recovered remains for every unknown soldier killed in the Vietnam War will be identified.

text: The Vietnam Unknown service member was originally designated by Medal of Honor recipient U.S. Marine Corps Sgt. Maj. Allan Jay Kellogg, Jr., during a ceremony at Pearl Harbor, Hawaii, May 17, 1984.

text: Each branch of the Armed Services took part in the transportation to honor the unknown. The Marines from Marine Barracks Hawaii consisted of an Honor Guard of 9 enlisted men and Lt. Denis Muller. The designated Vietnam Unknown was transported aboard the USS Brewton, where the Marines stood guard over the casket during the voyage to Naval Air Station Alameda, California. At Travis, the debarkation ceremony turned the remains over to the USAF on May 24. The next day, the remains of were flown from Travis Air Force Base, California, arriving at Andrews Air Force Base, Maryland. Once there the remains were turned over to the US Army, where the remains were taken to Fort McNair for placement upon the horse-drawn wagon which later carried the Unknown to the Capital Rotunda for display before interment.  While on display for public viewing, all branches of the US Armed Forces stood in honor, guarding the casket of the Unknown for 2 weeks.

text: Many Vietnam veterans and President Ronald Reagan and Nancy Reagan visited the Vietnam Unknown in the U.S. Capitol. An Army caisson carried the Vietnam Unknown from the Capitol to the Memorial Amphitheater at Arlington National Cemetery on Memorial Day, May 28, 1984.

text: President Reagan presided over the funeral, and presented the Medal of Honor to the Vietnam Unknown, and also acted as next of kin by accepting the interment flag at the end of the ceremony. The interment flags of all Unknowns at the Tomb of the Unknowns are on view in the Memorial Display Room.

text: Identification of the Unknown[edit]

text: In 1994, Ted Sampley, a POW/MIA activist, determined that the remains of the Vietnam Unknown were likely those of Air Force 1st Lt. Michael Joseph Blassie, who was shot down near An Lộc, Vietnam, in 1972. Sampley published an article in his newsletter and contacted Blassie's family, who attempted to pursue the case with the Air Force's casualty office without result. In January 1998, CBS News broadcast a report based on Sampley's investigation which brought political pressure to support the identification of the remains.[16] The body was exhumed on May 14, 1998. Based on mitochondrial DNA testing, Department of Defense scientists confirmed the remains were those of Blassie. The identification was announced on June 30, 1998, and on July 10, Blassie's remains arrived home to his family in St. Louis, Missouri; he was reinterred at Jefferson Barracks National Cemetery on July 11.[17][nb 4]

text: Redesignation of the crypt[edit]

text: The slab over the crypt that once held the remains of the Vietnam Unknown has since been replaced. The original inscription of "Vietnam" and the dates of the conflict has been changed to "Honoring and Keeping Faith with America's Missing Servicemen" as a reminder of the commitment of the Armed Forces to the fullest possible accounting of missing service members.

text: Tomb guards[edit]

text: The tomb guards are soldiers of the United States Army. The first military guards were troopers from the 3rd Cavalry, "Brave Rifles", who were posted nearby on Fort Myer. Since April 6, 1948, (known then as "Army Day"), when the regiment was reactivated, it has been guarded by soldiers from 3rd Infantry Regiment, "The Old Guard". The Old Guard is also posted to Fort Myer, Virginia, adjacent to Arlington National Cemetery. It is considered one of the highest honors to serve as a Sentinel at the Tomb of the Unknowns. Fewer than 20 percent of all volunteers are accepted for training and of those only a fraction pass training to become full-fledged Tomb Guards. This attrition rate has made the Tomb of the Unknown Soldier Guard Identification Badge the second least-awarded qualification badge of the United States military (the first being the Astronaut Badge).[18]

text: The soldier "walking the mat" does not wear rank insignia, so as not to outrank the Unknowns, whatever their ranks may have been. Non-commissioned officers (usually the Relief Commander and Assistant Relief Commanders), do wear insignia of their rank when changing the guard only. They have a separate uniform (without rank) that is worn when they actually guard the Unknowns or are "posted."

text: The duties of the sentinels are not purely ceremonial. The sentinels will confront people who cross the barriers at the tomb or who they perceive to be disrespectful or excessively loud.

text: Weapons[edit]

text: Over the years there have been several different types of weapons used by the tomb guards. The changes in weapons reflect the changes in the Army, including M1903 Springfield rifle, M1 Garand and M14 rifles, M1911 and M9 pistols. Tomb guards currently carry M14 rifles, which are affixed to ceremonial rifle stocks. These rifles are cleaned daily and kept ready for use at all times.[19]

text: Walking the mat[edit]

text: There is a meticulous routine that the guard follows when watching over the graves.[20] The tomb guard:

text:
Marches 21 steps south down the black mat laid across the Tomb.
Turns and faces east, toward the Tomb, for 21 seconds.
Turns and faces north, changes weapon to outside shoulder, and waits 21 seconds.
Marches 21 steps down the mat.
Turns and faces east for 21 seconds.
Turns and faces south, changes weapon to outside shoulder, and waits 21 seconds.
Repeats the routine until the soldier is relieved of duty at the Changing of the Guard.

text: After each turn, the guard executes a sharp "shoulder-arms" movement to place the weapon on the shoulder closest to the visitors to signify that the guard stands between the Tomb and any possible threat.

text: Out of respect for the interred, the sentinels command silence at the tombs. If the guard walking the mat must vocally confront a disturbance from spectators, or a threat, the routine is interrupted, and remains so until the disturbance is under control. The sentinel will exit the mat, place the weapon in port arms position, and confront the disturbance. Once under control, the sentinel then walks on the pavement to the other side of the mat, turns to shoulder arms, and continues the routine.

text: Twenty-one was chosen because it symbolizes the highest military honor that can be bestowed—the 21-gun salute.

text: The mat is usually replaced twice per year: before Memorial Day and before Veterans Day. This is required because of the wear on the rubber mat by the special shoes worn by tomb guards. The sentinels have metal plates built into the soles and inner parts of their shoes to allow for a more rugged sole and to give the signature click of the heel during maneuvers. The sentinels wear sunglasses because of the bright reflection from the marble surrounding the Tomb and the Memorial Amphitheater.

text: On the ground not covered by the mat, a rust pattern in the tile can be seen that corresponds to the precise steps taken during the changing of the guard. The metal from the guards' boots causes the brown rust markings on the stone. On the mat itself, footprints caused by standing guard are also visible.

text: Changing of the Guard[edit]

text: While Arlington National Cemetery is open, during the day in summer months from April 1 to September 30, the guard is changed every half hour. During the winter months, from October 1 to March 31, the guard is changed every hour. After the cemetery closes to the public (7 p.m. to 8 a.m. April through September, and 5 p.m. to 8 a.m. October through March), the guard is changed every 2 hours. The ceremony can be witnessed by the public whenever Arlington National Cemetery is open.[21][22]

text: The guard change is very symbolic, but also conducted in accordance with Army regulations. The relief commander or assistant relief commander, along with the oncoming guard, are both required for a guard change to take place. The relief commander orders the guard being relieved to "pass on your orders" to the oncoming guard. The guard being relieved will say to the oncoming guard, "Post and orders remain as directed." The oncoming guard's response is always, "Orders acknowledged." During changes when the public is witnessing the ceremony, the commander will inform the public that the ceremony is about to take place and that those in attendance should remain "silent and standing" throughout the entire event.

text: Dedication[edit]

text: A civilian guard was first posted at the Tomb on November 17, 1925, to prevent, among other things, families from picnicking on the flat marble slab with views of the city. A military guard was first posted on March 25, 1926. The first 24-hour guard was posted on midnight, July 2, 1937. The Tomb of the Unknowns has been guarded continuously, 24 hours a day, 7 days a week, since that time.[23] Inclement weather,[24][25] terrorist attacks,[26] et cetera, do not cause the watch to cease.[27]

text: Since 1948, the tomb guards, a special platoon within the 3rd U.S. Infantry Regiment (The Old Guard) work on a team rotation of 24 hours on, 24 hours off, for five days, taking the following four days off. A guard takes an average of six hours to prepare his uniform – heavy wool, regardless of the time of year – for the next day's work. In addition to preparing the uniform, guards also conduct physical training, tomb guard training, participate in field exercises, cut their hair before the next work day, and at times are involved in regimental functions as well. Tomb guards are required to memorize 35 pages of information about Arlington National Cemetery and the Tomb of the Unknown Soldier, including the locations of nearly 300 graves and who is buried in each one.[21]

text: A special Army decoration, the Tomb of the Unknown Soldier Guard Identification Badge is authorized for wear after passing a detailed test of 100 questions (from a pool of more than 300), a uniform test with two gigs (errors) or fewer (measured to the 1/64"), and a test on the guard changing sequence. After serving honorably for a period of nine months, and having passed the sequence of tests, a tomb guard is permanently awarded the Badge. Since the first award on February 7, 1958, fewer than 650 soldiers have completed training and been awarded this badge, including four women. A small number of tomb guard Identification Badges have also been retroactively awarded to soldiers who served as Guards before 1959. Those numbers make the Badge the second rarest award currently issued in the United States Army; only the Army Astronaut Badge is rarer.[nb 5]

text: The badge was designed in 1956 and first issued to members of the Honor Guard at the Tomb of the Unknowns on February 7, 1958. The badge was first issued only as a temporary wear item, meaning the soldiers could only wear the badge during their tenure as members of the honor guard. Upon leaving the duty, the badge was returned and reissued to incoming soldiers. In 1963, a regulation was enacted that allowed the badge to be worn as a permanent part of the military uniform, even after the soldier's completion of duty at the Tomb of the Unknowns.

text: Damage and repair to the Tomb Monument[edit]

text: Cracking and weathering are causing concerns for the long-term preservation of the Tomb Monument. A November 1963 report first recorded horizontal cracking of the monument's marble die block. Though this was the first time that the damage was documented, the report made it clear that the cracks had become visible some time before that date.[28]

text: In 1963–1964, there were two cracks—referred to as "primary" and "secondary"—extending approximately 34 feet around the die block. By 1974, they had extended to 40 feet. They grew another 4.6 feet over the next 15 years. Inspection has determined that the cracks have increased horizontally since 1990. Analysis also indicates that the cracks are not surficial  but extend partially through the block and will eventually extend all the way through.[28]

text: The 1990 report documented deterioration of the marble's surface. As much as 2.85 mm of the marble surface has been lost through weathering. The study projected that before 2010, the Tomb Monument will have been weathered enough to have a negative effect on the experience of the visitors and concludes the only solutions are to enclose or replace the monument.[28]

text: Several options have been considered to deal with the damage. Officials at Arlington National Cemetery determined that proper repair can return the Tomb Monument to an acceptable appearance. However, because the cracks will continue to lengthen and widen, continuous grouting, regrouting, touch-up, monitoring, and maintenance would be required. Therefore, a report commissioned by Arlington National Cemetery and published in June 2006 confirmed the Cemetery's conclusion that "replacement of the three pieces of the Tomb Monument is the preferred alternative". A final decision was scheduled to be made on September 30, 2007.[28]

text: The National Trust for Historic Preservation objects to the plan to replace the authentic Tomb Monument. The Trust expressed concern that Arlington National Cemetery seeks to replace the existing monument with marble from the original quarry, which experts agree is likely eventually to crack.[29]

text: The Trust has observed that the Cemetery's own 1990 report recommended that the monument be repaired and that the Cemetery, in fact, commissioned Oehrlein Architects to repair the stone. In 2007, Mary Oehrlein informed Congressional staff members that: "The existing monument can easily be repaired, as was done 17 years ago, using conventional conservation methods to re-grout the cracks. Once repaired, the fault lines would be virtually invisible from the public viewing areas."[30][31]

text: On September 26, 2007, U.S. Senator Daniel Akaka announced that an amendment crafted together with Senator Jim Webb will be added to the National Defense Authorization Act for Fiscal Year 2008 (H.R. 1585) that would require a report on the plans of the Secretary of the Army and the Secretary of Veterans Affairs to replace the monument at the Tomb of the Unknowns. The secretaries would be required to advise Congress on the current efforts to maintain and preserve the monument. Additionally, they would have to provide an assessment on the feasibility and advisability of repairing rather than replacing the Tomb Monument. Finally, if the secretaries choose replacement, they would have to report those plans and detail how they intend to dispose of the current monument. Once the report is provided, the secretaries are prevented from taking action to replace the monument for at least 180 days. The Akaka-Webb amendment was included in the bill by unanimous consent of the Senate.[32] An amendment to the Fiscal Year 2008 Defense Authorization Bill authorized a review of the monument's condition. The bill also authorized repair, but not replacement, of the monument.[33] Final passage of the National Defense Authorization Act for 2008 (H.R. 4986) was signed by President Bush on January 28, 2008.

text: In 2003 John Haines, a retired car dealer, offered to donate a large slab of marble to the Arlington National Cemetery to replace the existing marble. Haines paid $31,000 for the marble slab.[34] The marble was not removed from the quarry, however, because imperfections were found and the block was rejected.

text: In June 2009 Arlington National Cemetery and the U.S. Army Corps of Engineers announced that the monument was to be repaired, not replaced.[35] In 2010, the cracks were filled but the repairs lasted only a few months.[36] As of June 2011, the cemetery was struggling to repair the cracks in the monument, one of which measured 28.4 feet (8.7 m) long, with another at 16.2 feet (4.9 m).[37] In September 2011, the cracks were filled again[36] and on October 21, 2011, inspection by the Corps of Engineers and other experts pronounced the repairs a success.[38]


document_title: Green Revolution in India

question_text: what was the primary objective of green revolution in india

root

text: Green Revolution in India

text: History[edit]

text: 49% of people in India are employed in agriculture.[citation needed]The introduction of high-yielding varieties of seeds after 1965 and the increased use of fertilizers and irrigation are known collectively as the Green Revolution, which provided the increase in production needed to make India self-sufficient in food grains. The program was started with the help of the United States-based Rockefeller Foundation and was based on high-yielding varieties of wheat, rice, and other grains that had been developed in Mexico and in the Philippines. Of the high-yielding seeds, wheat produced the best results. Production of coarse grains—the staple diet of the poor—and pulses—the main source of protein—lagged behind, resulting in reduced per capita availability.

tag: p

text: The total area under the high-yielding-varieties program was a negligible 1.9 million hectares in fiscal year 1960. Since then, growth has been spectacular, increasing to nearly 15.4 million hectares by FY 1970, 43.1 million hectares by FY 1980, and 63.9 million hectares by FY 1990. The rate of growth decreased significantly in the late 1980s, however, as additional suitable land was not available (see table 32, Appendix).

text: The major benefits of the Green Revolution were experienced mainly in northern and northwestern India between 1965 and the early 1980s; the program resulted in a substantial increase in the production of food grains, mainly wheat and rice. Food-grain yields continued to increase throughout the 1980s, but the dramatic changes in the years between 1965 and 1980 were not duplicated. By FY 1980, almost 75 percent of the total cropped area under wheat was sown with high-yielding varieties. For rice the comparable figure was 45 percent. In the 1980s, the area under high-yielding varieties continued to increase, but the rate of growth overall was slower. The eighth plan aimed at making high-yielding varieties available to the whole country and developing more productive strains of other crops.

text: The Green Revolution created wide regional and interstate disparities. The plan was implemented only in areas with assured supplies of water and the means to control it, large inputs of fertilizers, and adequate farm credit. These inputs were easily available in at least parts of the states of Punjab, Haryana, and western Uttar Pradesh; thus, yields increased most in these states. In other states, such as Andhra Pradesh and Tamil Nadu, in areas where these inputs were not assured, the results were limited or negligible, leading to considerable variation in crop yields within these states. The Green Revolution also increased income disparities: higher income growth and reduced incidence of poverty were found in the states where yields increased the most and lower income growth and little change in the incidence of poverty in other states.

text: Practices[edit]

text: Wheat[edit]

text: The main development was higher-yielding varieties of wheat,[1] for developing rust resistant strains of wheat.[2] The introduction of high-yielding varieties(HYV) of seeds and the increased quality of fertilizers and irrigation technique led to the increase in production to make the country self-sufficient in food grains, thus improving agriculture in India.[3] The methods adopted included the use of high-yielding varieties (HYVs) of seeds[4] with modern farming methods.

text: The production of wheat has produced the best results in fueling self-sufficiency of India. Along with high-yielding seeds and irrigation facilities, the enthusiasm of farmers mobilised the idea of agricultural revolution. Due to the rise in use of chemical pesticides and fertilizers, there was a negative effect on the soil and the land (e.g., land degradation).

text: Other practices[edit]

text: This section is in a list format that may be better presented using prose. You can help by converting this section to prose, if appropriate. Editing help is available. (January 2018)

tag: table

text:
Irrigation infrastructure
Use of pesticides

Use of insecticides
Use of herbicides

Consolidation of holdings
Land reforms
Improved rural infrastructure
Supply of agricultural credit
Use of chemical or synthetic fertilizers
Use of sprinklers or drip irrigational systems
Use of advanced machinery
Use of vector quantity

tag: ul

text: Problems that were addressed[edit]

text: Frequent famines[edit]

text: Famines in India were very frequent during the period 1940s to 1970s. Due to faulty distribution of food, and because farmers did not receive the true value for their labour, the majority of the population did not get enough food.[5] Malnutrition and starvation was a huge problem.[citation needed]

text: Lack of finance[edit]

text: Marginal farmers found it very difficult to get finance and credit at economical rates from the government and banks and hence, fell as easy prey to the money lenders. They took loans from zamindars, who charged high rates of interests and also exploited the farmers later on to work in their fields to repay the loans (farm labourers).[citation needed] Proper financing was not given during the Green Revolution period, which created a lot of problems and sufferings to the farmers of India. Government also helped those under loans.

text: Lack of self-sufficiency[edit]

text: Due to traditional agricultural practices, low productivity, and a growing population, often food grains were imported — draining scarce foreign reserves. It was thought that with the increased production due to the Green Revolution, the government could maintain buffer stock and India could achieve self-sufficiency and self-reliability.[citation needed]

text: Agriculture was basically for subsistence and, therefore, less agricultural product was offered for sale in the market. Hence, the need was felt to encourage the farmers to increase their production and offer a greater portion of their products for sale in the market. The new methods in agriculture increased the yield of rice and wheat, which reduced India's dependence on food imports.

text: Criticisms[edit]

text: Indian Economic Sovereignty[edit]

text: A main criticism of the effects of the green revolution is the cost for many small farmers using HYV seeds, with their associated demands of increased irrigation systems and pesticides. A case study is found in India, where farmers are buying Monsanto BT cotton seeds—sold on the idea that these seeds produced 'natural insecticides'. In reality, they need to still pay for expensive pesticides and irrigation systems, which might lead to increased borrowing to finance the change from traditional seed varieties. Many farmers have difficulty in paying for the expensive technologies, especially if they have a bad harvest.

text: Indian environmentalist Vandana Shiva notes that this is the "second Green Revolution". The first Green Revolution, she suggests, was mostly publicly funded (by the Indian Government). This new Green Revolution, she says, is driven by private (and foreign) interest – notably MNCs like Monsanto. Ultimately, this is leading to foreign ownership over most of India's farmland.[6] [7]

text: Environmental Damage[edit]

text: Excessive and inappropriate use of fertilizers and pesticides has polluted waterway, killed beneficial insects and wild life. It has caused over-use of soil and rapidly depleted its nutrients. The rampant irrigation practices have led to eventually soil degradation. Groundwater practices have fallen dramatically. Further, heavy dependence on few major crops has led to loss of biodiversity of farmers. These problems were aggravated due to absence of training to use modern technology and vast illiteracy leading to excessive use of chemicals.[1]

text: Increased Regional disparities[edit]

text: Green revolution spread only in irrigated and high-potential rain fed areas. The villages or regions without the access of sufficient water were left out that widened the regional disparities between adopters and non-adopters. Since, the HYV seeds technically can be applied only in land with assured water supply and availability of other inputs like chemicals, fertilizers etc. The application of the new technology in the dry-land areas is simply ruled out.

text: The states like Punjab, Haryana, Western UP etc. having good irrigation and other infrastructure facilities were able to derive the benefits of green revolution and achieve faster economic development while other states have recorded slow growth in agriculture production.

text: Restrictive Crop Coverage[edit]

text: The new agriculture strategy involving use of HYV seeds was initially limited to wheat, maize and bajra. The other major crop i.e. rice responded much later. The progress of developing and application of HYV seeds in other crops especially commercial crops like oilseeds, jute etc. has been very slow. In fact, in certain period a decline in the output of commercial crops is witnessed because of diversion of area under commercial crop to food crop production. The basic factor for non-spread of green revolution to many crops was that in the early 1960s the severe shortage in food grains existed and imports were resorted to overcame the shortage. Government initiated green revolution to increase food grain productivity and non-food grain crops were not covered. The substantial rise in one or two food grain crop cannot make big difference in the total agricultural production. Thus new technology contributed insignificantly in raising the overall agricultural production due to limited crop coverage. So it is important that the revolutionary efforts should be made in all major crops.

text: Further reading[edit]

text: "The Great Gene Robbery" by Claude Alvares


document_title: Prime Minister of Pakistan

question_text: minimum age limit for prime minister in pakistan

text: Prime Minister of Pakistan

text: History[edit]

text: The office of the Prime Minister was created on immediate effect after the partition and the establishment of Pakistan in 1947; the Prime Minister existed alongside the Governor-General who was the representative of the British Monarchy. The first Prime Minister, Liaquat Ali Khan, exercised central executive powers until his assassination in 1951.[25] However, the powers slowly began to be reduced as a result of constant intervention by the Governor-General. Despite the first set of the Constitution giving central power in 1956, the next six prime ministers were dismissed by the Governor-General from 1951 till 1957. In addition, the first set of the Constitution had evolved the Governor-General into the President of Pakistan whilst declaring the country an "Islamic republic".[26][27] In 1958, President Iskandar Mirza dismissed the seventh prime minister to impose martial law in a mere two weeks, President Mirza was ousted by army chief General Ayub Khan who had for a brief period held the post of Prime Minister.

text: In 1962, the second set of the Constitution completely dissolved the office of prime minister as all powers were transferred to the President of Pakistan.[27][28] Criticism over the presidency after the presidential election held in 1965 over the centralizing of powers. After the general elections held in 1970, the office was established with Nurul Amin becoming the Prime Minister who was also the Vice-President. Negotiations that fall apart between Zulfikar Ali Bhutto, Mujibur Rehman, and Yahya Khan that prompted to liberation movement in the East Pakistan. With India intervening in East Pakistan and Pakistan conceding defeat to end the war led to the collapse of the presidential system in 1971.

text: As the comprehensive Constitution reinstated in 1973, the post was reestablished with more central powers as the constitution provided a parliamentary system with President of Pakistan as figurehead.[29] Amid agitation instigated by the right-wing alliance invited the military intervention in 1977 which suspended the post.

text: The general elections held in 1985 restored the post, with Muhammad Junejo becoming the Prime Minister. Later that year, the National Assembly passed the controversial eighth amendment to the Constitution, giving the President the power to dismiss the Prime Minister and the National Assembly without prior consultation.[30] The general elections in 1988 resulted in the Pakistan Peoples Party's Benazir Bhutto becoming the first woman Prime Minister elected in a Muslim country.[31]

text: From 1988 to 1993, the power struggle between the Prime Minister and Presidency continued with President dismissing the National Assembly on three different occasions. At the 1997 elections, the PML(N) secured a two-thirds majority in the Parliament and drafted the XIII and XIV Amendments to reverse the eighth amendment to the Constitution; this allowed Nawaz Sharif to centralize more executive powers.[32] After the draw down of civil-military relations in 1999, Chairman joint chiefs General Pervez Musharraf staged a coup d'état against the PML(N)'s government and held nationwide elections in 2002.[33]

text: With no party gaining a majority, a coalition was formed with the PML(Q) – a breakaway of the PML(N) and a pro-Musharraf party – leading with MQM. After some political wrangling, Zafarullah Jamali became the Prime Minister, and passed the XVII amendment which partially restored the power of the President to dissolve the National Assembly, but made the dissolution subject to the Supreme Court of Pakistan's approval.[34]

text: Over the authority issues,[clarification needed] Prime Minister Jamali resigned in 2004 and Shaukat Aziz was eventually appointed as Prime Minister, securing 151 out of 191 votes in the National Assembly.[35] The XVII amendment featured a semi-presidential system allowing the presidency to keep the interference[clarification needed] executive and the judiciary.[34] The general elections in 2008 resulted in the PPP coming to power and supporting the movement to oust Pervez Musharraf.[36] A populist intellectual movement leading to the departure of Pervez Musharraf allowed Asif Zardari to become President. In 2010, the XVIII Amendment to the Constitution of Pakistan was passed to reverse the XVII amendment; it returned the country to being a parliamentary democratic republic. In addition, the XVIII Amendment removed all powers of the presidency to dissolve the Parliament unilaterally and sweep away the powers amassed by the former presidents Pervez Musharraf and Zia-ul-Haq to maintain a delicate check and balance.[37]

text: Following a contempt of court case, the Supreme Court permanently disqualified Prime Minister Yousuf Raza Gillani.[38] Originally, the PPP nomination was Makhdoom Shahbuddin,[39] but he was forced to withdraw after the ANF issued non-bailable arrest warrants against him.[40] Raja Pervaiz Ashraf became the Prime Minister and remained in office until 2013.[40][41][42][23] The general election held in 2013 saw the PML(N) almost achieve a supermajority. Following this, Nawaz Sharif was elected as Prime Minister, returning to the post for the third time after a fourteen-year absence, in a democratic transition. In 2017, Sharif was forced to step down as prime minister following corruption charges against him.[citation needed]

text: On August 18, 2018, Imran Khan was sworn in as the country's 21st prime minister.[43]

text: Constitutional law[edit]

text:
Pakistan
This article is part of a series on thepolitics and government ofPakistan
Constitution[show]
Previous constitutions:195619621973
Annex (written 1949, incorporated 1985)
Amendments
Law

Government[show]
President (list): Arif Alvi

Parliament

Senate
Chairman: Sadiq Sanjrani
Deputy Chairman: Saleem Mandviwalla
National Assembly
Speaker: Asad Qaiser
Deputy Speaker: Qasim Suri

Executive:

Prime Minister (list): Imran Khan
Federal Cabinet
Federal Agencies
Civil Service

Judiciary

Supreme Judicial Council
Supreme Court
Chief Justice
Federal Shariat Court
Supreme Appellate Court Gilgit-Baltistan
Chief Justices
Islamabad High Court
Provincial High Courts
Chief Court Gilgit-Baltistan
District Courts

Elections[show]
Election Commission
Electoral College
Recent elections
Presidential: 201820132008
General: 201820132008
Political parties
Pakistan Tehreek-e-Insaf
Pakistan Muslim League (N)
Pakistan Peoples Party

Administrative units[show]
Provinces
Balochistan
Khyber Pakhtunkhwa
Punjab
Sindh
Territories
Islamabad
Autonomous region
Azad Kashmir
Gilgit–Baltistan

Federalism[show]
Azad Kashmir government
President
Prime Minister
Legislative Assembly
Provincial governments
Governors
Chief Ministers
Provincial Assemblies
Local government
Divisions
Districts
Tehsils
Union councils

Foreign relations[show]
China - Pakistan relations
India–Pakistan relations
Pakistan United States relations
Kashmir conflict
Embassies

Other countries
Atlas
vte

text: The Constitution envisages a scheme of affairs in which the President of Pakistan is the head of state who represents the "unity of the Republic." The system of government in Pakistan is based on codified constitution which sees the Prime Minister as "chief executive of the Republic."

text: Subject to the Constitution, the executive authority of the Federation shall be exercised in the name of the President by the Federal Government, consisting of the Prime Minister and the Federal Ministers, which shall act through the Prime Minister, who shall be the chief executive of the Federation."

text: In addition, the Prime Minister is also the chairman of the Council of Common Interests as set by:

text: (1) There shall be a Council of Common Interests, in this Chapter referred to as the Council, to be appointed by the President

text:
(2)  The Council shall consist of-
(a)  the Prime Minister who shall be the Chairman of the Council;
(b)  the Chief Ministers of the Provinces;

text: (c)  three members from the Federal Government to be nominated by the Prime Minister from time to time.

text: As in most of the parliamentary democracies, a head of state's duties are mostly ceremonial. The Prime Minister of Pakistan is the head of government and has the responsibility for executive power. With Pakistan following a parliamentary system of government, the Prime minister is generally the leader of a party (or coalition of parties) that has a majority in the National Assembly —the lower house of the Parliament of Pakistan. The Prime Minister, in common with all other ministers, either has to be a current member of National Assembly, or be elected within six months of being appointed.[44]

text: Role and powers of the Prime minister[edit]

text: The official residence and principal workplace of the Prime Minister is the Prime Minister's Office located in northeast Islamabad. The Prime Minister is the Chief Executive who heads and exercises the authority of the Government of Pakistan. After obtaining a vote of confidence, the Prime Minister is invited by the President to take the oath of office and form the government.[44] In practice, the Prime Minister nominates the members of the Cabinet who supervise the important functions and ministries of the Government of Pakistan.[44] In addition, the Prime Minister communicates to the President all decisions of the Cabinet relating to the administration of affairs of state and proposals for legislation.[46]

text:
The Prime Minister, in consultation with the Cabinet, schedules and attends the sessions of the Parliament and is required to answer questions from Members of Parliament to the ministers.
The Prime Minister makes appointments on various important positions, including:

text:
The federal secretaries as head of cabinet-level ministries
The chief secretaries of the provinces
Key administrative and military personnel in the Pakistan Armed Forces
The chairmen of large public sector organisations and corporations such as NHA, PIA, PNSC etc
The chairmen and other members of the federal commissions and public institutions
Ambassadors and High Commissioners to other countries

text: Some specific ministries/department are not allocated to anyone in the cabinet but the prime minister himself. The prime minister is usually always in-charge/Chairman of:

text:
Planning Commission
National Command Authority
National Security Council
Economic Coordination Committee
Cabinet Committee on National Security

text: The Prime Minister is vested with command authority over the Pakistani nuclear arsenals and represents the country in various delegations, high-level meetings and international organisations that require the attendance of the highest government office and also addresses the nation on various issues of national importance.[19]

text: Eligibility[edit]

text: The Constitution of Pakistan requires that the Prime Minister be a member of the National Assembly.[47]  As well as this, one must:

text:
be a citizen of Pakistan.
be a Muslim
be above 25 years of age
be able to prove good conduct of character and be not commonly known to violate Islamic injunctions
have adequate knowledge of Islamic teachings and practice obligatory duties prescribed by Islam, as well as abstaining from major sins
have not, after the establishment of Pakistan, worked against the integrity of the country or opposed the ideology of Pakistan.

text: Selection and removal[edit]

text: The candidates for the prime minister are members of the National Assembly or Senate who were chosen through direct elections by popular vote following campaigning on the party platforms.[48] Usually, the leader of the majority party in the parliament retains the office of prime minister, and forms the government either by coalition or by simple majority.[49] The candidate must retain the vote of confidence of the members of the parliament before being invited by the President to form the government.[44]

text: The Prime Minister can be removed before the expiry of the term through a vote of no confidence in the parliament.[44] If the vote of no confidence is passed by the National Assembly by not less than 20%, the Prime Minister ceases to retain the office.[44] In the past, prime ministers (and their governments) have been dismissed by the President exercising the VIII Amendment to the Constitution of Pakistan (1985), but this was repealed by the XVIII Amendment to the Constitution of Pakistan (2010).[50][51] In addition, the Prime Minister himself has absolute constitutional immunity from criminal and civil proceedings, and no proceedings can be initiated or continued against him during the term of his office.[52]

text: In 2012, the Supreme Court of Pakistan has ceased at least one Prime Minister from retaining the office due to contempt of court after retroactively disqualifying the membership of the parliament permanently.[53][54]

text: On 28 July 2017, the Supreme Court of Pakistan disqualified the Prime Minister Nawaz Sharif from retaining the office due to his failure in fulfilling the eligibility requirements as enshrined in Articles 62 of the Constitution. This was in the aftermath of the Supreme Court hearing regarding the Panama Papers Case. This also resulted in him being permanently disqualified from membership of the parliament.[55]

text: The prime minister is elected by the National Assembly.[56] The National Assembly meets on the twenty-first day after a general election (at least every five years) unless the President calls for a vote of no confidence. Whichever member of the National assembly is chosen serves as the Prime Minister until the next election or until he fails to maintain the confidence of the National Assembly.

text: 91.  The Cabinet:

text: (1)  There shall be a Cabinet of Ministers, with the Prime Minister at its head, to aid and advise the President in the exercise of his functions.

text: (2)  The National Assembly shall meet on the twenty-first day following the day on which a general election to the Assembly is held unless sooner summoned by the President.

text: (3)  After the election of the Speaker and the Deputy Speaker, the National Assembly shall, to the exclusion of any other business, proceed to elect without debate one of its Muslim members to be the Prime Minister.

text: (4)  The Prime Minister shall be elected by the votes of the majority of the total membership of the National Assembly:

text: Provided that, if no member secures such majority in the first poll, a second poll shall be held between the members who secure the two highest numbers of votes in the first poll and the member who secures a majority of votes of the members present and voting shall be declared to have been elected as Prime Minister:

text: Provided further that, if the number of votes secured by two or more members securing the highest number of votes is equal, further poll shall be held between them until one of them secures a majority of votes of the members present and voting.

text: (5)  The member elected under clause (4) shall be called upon by the President to assume the office of Prime Minister and he shall, before entering upon the office, make before the President oath in the form set out in the Third Schedule:

text: Provided that there shall be no restriction on the number of terms for the office of the Prime Minister.

text: Oath of office[edit]

text: The Prime Minister is required to make and subscribe to, in the presence of the President, an oath or affirmation that they shall protect, preserve and defend the Constitution as follows:

text: I, ____________, do swear solemnly that l am a Muslim and believe in the Unity and Oneness of Almighty Allah, the Books of Allah, the Holy Qura'an being the last of them, the Prophethood of Muhammad (peace be upon him) as the last of the Prophets and that there can be no Prophet after him, the Day of Judgment, and all the requirements and teachings of the Holy Quran and Sunnah:

text: That I will bear true faith and allegiance to Pakistan:

text: That, as Prime Minister of Pakistan, I will discharge my duties, and perform my functions, hon-estly, to the best of my ability, faithfully in accordance with the Constitution of the Islamic Republic of Pakistan and the law, and always in the interest of the sovereignty, integrity, solidarity, well- being and prosperity of Pakistan:

text: That I will strive to preserve the Islamic Ideology which is the basis for the creation of Pakistan:

text: That I will not allow my personal interest to influence my official conduct or my official decisions:

text: That I will preserve, protect and defend the Constitution of the Islamic Republic of Pakistan:

text: That, in all circumstances, I will do right to all manner of people, according to law, without fear or favor, affection or ill- will:

text: And that I will not directly or indirectly communicate or reveal to any person any matter which shall be brought under my consideration or shall become known to me as Prime Minister except as may be required for the due discharge of my duties as Prime Minister.

text: May Allah Almighty help and guide me (A'meen).

text: Past Prime Ministers[edit]

text: Chronological list of Prime Ministers with tenure[edit]

text:
Living former prime ministers

Z.K. Jamali(PML-Q) 15th, served 2002–2004  (1944-01-01) January 1, 1944 (age 74)

Shujaat Hussain(PML-Q) 16th, served 2004  (1946-01-27) January 27, 1946 (age 72)

Shaukat Aziz(PML-Q) 17th, served 2004–2007  (1949-03-06) March 6, 1949 (age 69)

Yousaf Raza Gillani(PPP) 18th, served 2008–2012  (1952-07-09) July 9, 1952 (age 66)

Nawaz Sharif(PML-N) 12th,14th and 20th served 1990–1993, 1993, 1997–1999, 2013–2017  (1949-12-25) December 25, 1949 (age 68)

Shahid Khaqan Abbasi(PML-N) 21st, served 2017–2018  (1958-12-27) December 27, 1958 (age 59)


document_title: Effect size

question_text: a cohen's d of –0.19 is what type of effect size

question_tokens: a cohen 's d of -- 0.19 is what type of effect size

text: Effect size

text: Overview[edit]

text: Population and sample effect sizes[edit]

text:
The term effect size can refer to the value of a statistic calculated from a sample of data, the value of a parameter of a hypothetical statistical population, or to the equation that operationalizes how statistics or parameters lead to the effect size value.[1] Conventions for distinguishing sample from population effect sizes follow standard statistical practices — one common approach is to use Greek letters like ρ to denote population parameters and Latin letters like r to denote the corresponding statistic; alternatively, a "hat" can be placed over the population parameter to denote the statistic, e.g. with

ρ
^

{\displaystyle {\hat {\rho }}}

 being the estimate of the parameter

ρ

{\displaystyle \rho }

.

text: As in any statistical setting, effect sizes are estimated with sampling error, and may be biased unless the effect size estimator that is used is appropriate for the manner in which the data were sampled and the manner in which the measurements were made. An example of this is publication bias, which occurs when scientists only report results when the estimated effect sizes are large or are statistically significant. As a result, if many researchers carry out studies with low statistical power, the reported effect sizes will tend to be larger than the true (population) effects, if any.[5] Another example where effect sizes may be distorted is in a multiple trial experiment, where the effect size calculation is based on the averaged or aggregated response across the trials.[6]

text: Relationship to test statistics[edit]

text: Sample-based effect sizes are distinguished from test statistics used in hypothesis testing, in that they estimate the strength (magnitude) of, for example, an apparent relationship, rather than assigning a significance level reflecting whether the magnitude of the relationship observed could be due to chance. The effect size does not directly determine the significance level, or vice versa. Given a sufficiently large sample size, a non-null statistical comparison will always show a statistically significant results unless the population effect size is exactly zero (and even there it will show statistical significance at the rate of the Type I error used). For example, a sample Pearson correlation coefficient of 0.01 is statistically significant if the sample size is 1000. Reporting only the significant p-value from this analysis could be misleading if a correlation of 0.01 is too small to be of interest in a particular application.

text: Standardized and unstandardized effect sizes[edit]

text: The term effect size can refer to a standardized measure of effect (such as r, Cohen's d, or the odds ratio), or to an unstandardized measure (e.g., the difference between group means or the unstandardized regression coefficients). Standardized effect size measures are typically used when:

text:
the metrics of variables being studied do not have intrinsic meaning (e.g., a score on a personality test on an arbitrary scale),
results from multiple studies are being combined,
some or all of the studies use different scales, or
it is desired to convey the size of an effect relative to the variability in the population.

text: In meta-analyses, standardized effect sizes are used as a common measure that can be calculated for different studies and then combined into an overall summary.

text: Types[edit]

text: About 50 to 100 different measures of effect size are known.

text: Correlation family: Effect sizes based on "variance explained"[edit]

text: These effect sizes estimate the amount of the variance within an experiment that is "explained" or "accounted for" by the experiment's model.

text: Pearson r or correlation coefficient[edit]

text: Pearson's correlation, often denoted r and introduced by Karl Pearson, is widely used as an effect size when paired quantitative data are available; for instance if one were studying the relationship between birth weight and longevity. The correlation coefficient can also be used when the data are binary. Pearson's r can vary in magnitude from −1 to 1, with −1 indicating a perfect negative linear relation, 1 indicating a perfect positive linear relation, and 0 indicating no linear relation between two variables. Cohen gives the following guidelines for the social sciences:[7][8]

text:
Effect size
r

Small
0.10

Medium
0.30

Large
0.50

text: Coefficient of determination[edit]

text: A related effect size is r2, the coefficient of determination (also referred to as R2 or "r-squared"), calculated as the square of the Pearson correlation r. In the case of paired data, this is a measure of the proportion of variance shared by the two variables, and varies from 0 to 1. For example, with an r of 0.21 the coefficient of determination is 0.0441, meaning that 4.4% of the variance of either variable is shared with the other variable. The r2 is always positive, so does not convey the direction of the correlation between the two variables.

text: Eta-squared (η2)[edit]

text: Eta-squared describes the ratio of variance explained in the dependent variable by a predictor while controlling for other predictors, making it analogous to the r2. Eta-squared is a biased estimator of the variance explained by the model in the population (it estimates only the effect size in the sample). This estimate shares the weakness with r2 that each additional variable will automatically increase the value of η2. In addition, it measures the variance explained of the sample, not the population, meaning that it will always overestimate the effect size, although the bias grows smaller as the sample grows larger.

text: Omega-squared (ω2)[edit]

text: A less biased estimator of the variance explained in the population is ω2[9][10][11]

text: This form of the formula is limited to between-subjects analysis with equal sample sizes in all cells.[11] Since it is less biased (although not unbiased), ω2 is preferable to η2; however, it can be more inconvenient to calculate for complex analyses. A generalized form of the estimator has been published for between-subjects and within-subjects analysis, repeated measure, mixed design, and randomized block design experiments.[12] In addition, methods to calculate partial Omega2 for individual factors and combined factors in designs with up to three independent variables have been published.[12]

text: Cohen's ƒ2[edit]

text: Cohen's ƒ2 is one of several effect size measures to use in the context of an F-test for ANOVA or multiple regression. Its amount of bias (overestimation of the effect size for the ANOVA) depends on the bias of its underlying measurement of variance explained (e.g., R2, η2, ω2).

text: The ƒ2 effect size measure for multiple regression is defined as:

text: Likewise, ƒ2 can be defined as:

text:
The

f

2

{\displaystyle f^{2}}

 effect size measure for sequential multiple regression and also common for PLS modeling[14] is defined as:

text:
Cohen's

f
^

{\displaystyle {\hat {f}}}

 can also be found for factorial analysis of variance (ANOVA) working backwards using :

text:
In a balanced design (equivalent sample sizes across groups) of ANOVA, the corresponding population parameter of

f

2

{\displaystyle f^{2}}

 is

text: wherein μj denotes the population mean within the jth group of the total K groups, and σ the equivalent population standard deviations within each groups. SS is the sum of squares in ANOVA.

text: Cohen's q[edit]

text: Another measure that is used with correlation differences is Cohen's q. This is the difference between two Fisher transformed Pearson regression coefficients. In symbols this is

text: where r1 and r2 are the regressions being compared. The expected value of q is zero and its variance is

text: where N1 and N2 are the number of data points in the first and second regression respectively.

text: Difference family: Effect sizes based on differences between means[edit]

text: A (population) effect size θ based on means usually considers the standardized mean difference between two populations[15]:78

text: where μ1 is the mean for one population, μ2 is the mean for the other population, and σ is a standard deviation based on either or both populations.

text: In the practical setting the population values are typically not known and must be estimated from sample statistics. The several versions of effect sizes based on means differ with respect to which statistics are used.

text:
This form for the effect size resembles the computation for a t-test statistic, with the critical difference that the t-test statistic includes a factor of

n

{\displaystyle {\sqrt {n}}}

. This means that for a given effect size, the significance level increases with the sample size. Unlike the t-test statistic, the effect size aims to estimate a population parameter and is not affected by the sample size.

text: Cohen's d [edit]

text: Cohen's d is defined as the difference between two means divided by a standard deviation for the data, i.e.

text: Jacob Cohen defined s, the pooled standard deviation, as (for two independent samples):[7]:67

text: where the variance for one of the groups is defined as

text: and similar for the other group.

text: The table below contains descriptors for magnitudes of d = 0.01 to 2.0, as initially suggested by Cohen and expanded by Sawilowsky.[16]

text:
Effect size
d
Reference

Very small
0.01
Sawilowsky, 2009

Small
0.20
Cohen, 1988

Medium
0.50
Cohen, 1988

Large
0.80
Cohen, 1988

Very large
1.20
Sawilowsky, 2009

Huge
2.0
Sawilowsky, 2009

text: Other authors choose a slightly different computation of the standard deviation when referring to "Cohen's d" where the denominator is without "-2"[17][18]:14

text: This definition of "Cohen's d" is termed the maximum likelihood estimator by Hedges and Olkin,[15] and it is related to Hedges' g by a scaling factor (see below).

text: So, in the example above of visiting England and observing men's and women's heights, the data (Aaron, Kromrey,& Ferron, 1998, November; from a 2004 UK representative sample of 2436 men and 3311 women) are:

text:
Men: mean height = 1750 mm; standard deviation = 89.93 mm
Women: mean height = 1612 mm; standard deviation = 69.05 mm

text: The effect size (using Cohen's d) would equal 1.756 (note that in the article a value of 1.72 (95% confidence intervals: 1.66 – 1.78) is found because the root mean square of the variances was used rather than the s as calculated above). This is very large and you should have no problem in detecting that there is a consistent height difference, on average, between men and women.

text: With two paired samples, we look at the distribution of the difference scores. In that case, s is the standard deviation of this distribution of difference scores. This creates the following relationship between the t-statistic to test for a difference in the means of the two groups and Cohen's d:

text: and

text: Cohen's d is frequently used in estimating sample sizes for statistical testing. A lower Cohen's d indicates the necessity of larger sample sizes, and vice versa, as can subsequently be determined together with the additional parameters of desired significance level and statistical power.[19]

text: Glass' Δ[edit]

text: In 1976 Gene V. Glass proposed an estimator of the effect size that uses only the standard deviation of the second group[15]:78

text: The second group may be regarded as a control group, and Glass argued that if several treatments were compared to the control group it would be better to use just the standard deviation computed from the control group, so that effect sizes would not differ under equal means and different variances.

text: Under a correct assumption of equal population variances a pooled estimate for σ is more precise.

text: Hedges' g[edit]

text: Hedges' g, suggested by Larry Hedges in 1981,[20] is like the other measures based on a standardized difference[15]:79

text:
where the pooled standard deviation

s

∗

{\displaystyle s^{*}}

 is computed as:

text: However, as an estimator for the population effect size θ it is biased. Nevertheless, this bias can be approximately corrected through multiplication by a factor

text:
Hedges and Olkin refer to this less-biased estimator

g

∗

{\displaystyle g^{*}}

 as d,[15] but it is not the same as Cohen's d. The exact form for the correction factor J() involves the gamma function[15]:104

text: Ψ, root-mean-square standardized effect[edit]

text: A similar effect size estimator for multiple comparisons (e.g., ANOVA) is the Ψ root-mean-square standardized effect.[13] This essentially presents the omnibus difference of the entire model adjusted by the root mean square, analogous to d or g. The simplest formula for Ψ, suitable for one-way ANOVA, is

text: In addition, a generalization for multi-factorial designs has been provided.[13]

text: Distribution of effect sizes based on means[edit]

text:
Provided that the data is Gaussian distributed a scaled Hedges' g,

n

1

n

2

/

(

n

1

+

n

2

)

g

{\displaystyle {\sqrt {n_{1}n_{2}/(n_{1}+n_{2})}}\,g}

, follows a noncentral t-distribution with the noncentrality parameter

n

1

n

2

/

(

n

1

+

n

2

)

θ

{\displaystyle {\sqrt {n_{1}n_{2}/(n_{1}+n_{2})}}\theta }

 and (n1 + n2 − 2) degrees of freedom. Likewise, the scaled Glass' Δ is distributed with n2 − 1 degrees of freedom.

text: From the distribution it is possible to compute the expectation and variance of the effect sizes.

text: In some cases large sample approximations for the variance are used. One suggestion for the variance of Hedges' unbiased estimator is[15] :86

text: Other metrics[edit]

text: Mahalanobis distance (D) is a multivariate generalization of Cohen's d, which takes into account the relationships between the variables.[21]

text: Categorical family: Effect sizes for associations among categorical variables[edit]

text:
ϕ
=

χ

2

N

{\displaystyle \phi ={\sqrt {\frac {\chi ^{2}}{N}}}}

ϕ

c

=

χ

2

N
(
k
−
1
)

{\displaystyle \phi _{c}={\sqrt {\frac {\chi ^{2}}{N(k-1)}}}}

Phi (φ)
Cramér's V (φc)

text: Commonly used measures of association for the chi-squared test are the Phi coefficient and Cramér's V (sometimes referred to as Cramér's phi and denoted as φc). Phi is related to the point-biserial correlation coefficient and Cohen's d and estimates the extent of the relationship between two variables (2 x 2).[22] Cramér's V may be used with variables having more than two levels.

text: Phi can be computed by finding the square root of the chi-squared statistic divided by the sample size.

text: Similarly, Cramér's V is computed by taking the square root of the chi-squared statistic divided by the sample size and the length of the minimum dimension (k is the smaller of the number of rows r or columns c).

text: φc is the intercorrelation of the two discrete variables[23] and may be computed for any value of r or c. However, as chi-squared values tend to increase with the number of cells, the greater the difference between r and c, the more likely V will tend to 1 without strong evidence of a meaningful correlation.

text: Cramér's V may also be applied to 'goodness of fit' chi-squared models (i.e. those where c = 1). In this case it functions as a measure of tendency towards a single outcome (i.e. out of k outcomes). In such a case one must use r for k, in order to preserve the 0 to 1 range of V. Otherwise, using c would reduce the equation to that for Phi.

text: Cohen's w[edit]

text: Another measure of effect size used for chi square tests is Cohen's w. This is defined as

text: where p0i is the value of the ith cell under H0 and p1i is the value of the ith cell under H1.

text: Odds ratio[edit]

text: The odds ratio (OR) is another useful effect size. It is appropriate when the research question focuses on the degree of association between two binary variables. For example, consider a study of spelling ability. In a control group, two students pass the class for every one who fails, so the odds of passing are two to one (or 2/1 = 2). In the treatment group, six students pass for every one who fails, so the odds of passing are six to one (or 6/1 = 6). The effect size can be computed by noting that the odds of passing in the treatment group are three times higher than in the control group (because 6 divided by 2 is 3). Therefore, the odds ratio is 3. Odds ratio statistics are on a different scale than Cohen's d, so this '3' is not comparable to a Cohen's d of 3.

text: Relative risk[edit]

text: The relative risk (RR), also called risk ratio, is simply the risk (probability) of an event relative to some independent variable. This measure of effect size differs from the odds ratio in that it compares probabilities instead of odds, but asymptotically approaches the latter for small probabilities. Using the example above, the probabilities for those in the control group and treatment group passing is 2/3 (or 0.67) and 6/7 (or 0.86), respectively. The effect size can be computed the same as above, but using the probabilities instead. Therefore, the relative risk is 1.28. Since rather large probabilities of passing were used, there is a large difference between relative risk and odds ratio. Had failure (a smaller probability) been used as the event (rather than passing), the difference between the two measures of effect size would not be so great.

text: While both measures are useful, they have different statistical uses. In medical research, the odds ratio is commonly used for case-control studies, as odds, but not probabilities, are usually estimated.[24] Relative risk is commonly used in randomized controlled trials and cohort studies, but relative risk contributes to overestimations of the effectiveness of interventions.[25]

text: Risk difference[edit]

text: The risk difference (RD), sometimes called absolute risk reduction, is simply the difference in risk (probability) of an event between two groups. It is a useful measure in experimental research, since RD tells you the extent to which an experimental interventions changes the probability of an event or outcome. Using the example above, the probabilities for those in the control group and treatment group passing is 2/3 (or 0.67) and 6/7 (or 0.86), respectively, and so the RD effect size is 0.86 − 0.67 = 0.19 (or 19%). RD is the superior measure for assessing effectiveness of interventions.[25]

text: Cohen's h[edit]

text: One measure used in power analysis when comparing two independent proportions is Cohen's h. This is defined as follows

text:
h
=
2
(
arcsin

p

1

−
arcsin

p

2

)

{\displaystyle h=2(\arcsin {\sqrt {p_{1}}}-\arcsin {\sqrt {p_{2}}})}

text: where p1 and p2 are the proportions of the two samples being compared and arcsin is the arcsine transformation.

text: Common language effect size[edit]

text: To more easily describe the meaning of an effect size, to people outside statistics, the common language effect size, as the name implies, was designed to communicate it in plain English. It is used to describe a difference between two groups and was proposed, as well as named, by Kenneth McGraw and S. P. Wong in 1992.[26] They used the following example (about heights of men and women): "in any random pairing of young adult males and females, the probability of the male being taller than the female is .92, or in simpler terms yet, in 92 out of 100 blind dates among young adults, the male will be taller than the female",[27] when describing the population value of the common language effect size.

text: The population value, for the common language effect size, is often reported like this, in terms of pairs randomly chosen from the population. Kerby (2014) notes that a pair, defined as a score in one group paired with a score in another group, is a core concept of the common language effect size.[28]

text: As an other example, consider a scientific study (maybe of a treatment for some chronic disease, such as arthritis) with ten people in the treatment group and ten people in a control group. If everyone in the treatment group is compared to everyone in the control group, then there are (10×10=) 100 pairs. At the end of the study, the outcome is rated into a score, for each individual (for example on a scale of mobility and pain, in the case of an arthritis study), and then all the scores are compared between the pairs. The results, as the percent of pairs that support the hypothesis, is the common language effect size. In the example study it could be (lets say) .80, if 80 out of the 100 comparison pairs shows a better outcome for the treatment group, than the control group, and the report may read as follows: "When a patient in the treatment group was compared to a patient in the control group, in 80 of 100 pairs the treated patient showed a better treatment outcome." The sample value, in for example a study like this, is an unbiased estimator of the population value.[29]

text: Vargha and Delaney generalized the common language effect size (Vargha-Delaney A), to cover ordinal level data.[30] The R package orddom calculates A as well as bootstrap confidence intervals.

text: Rank-biserial correlation[edit]

text: An effect size related to the common language effect size is the rank-biserial correlation. This measure was introduced by Cureton as an effect size for the Mann–Whitney U test.[31] That is, there are two groups, and scores for the groups have been converted to ranks. The Kerby simple difference formula computes the rank-biserial correlation from the common language effect size.[28] Letting f be the proportion of pairs favorable to the hypothesis (the common language effect size), and letting u be the proportion of pairs not favorable, the rank-biserial r is the simple difference between the two proportions: r = f − u. In other words, the correlation is the difference between the common language effect size and its complement. For example, if the common language effect size is 60%, then the rank-biserial r equals 60% minus 40%, or r = 0.20. The Kerby formula is directional, with positive values indicating that the results support the hypothesis.

text: A non-directional formula for the rank-biserial correlation was provided by Wendt, such that the correlation is always positive.[32] The advantage of the Wendt formula is that it can be computed with information that is readily available in published papers. The formula uses only the test value of U from the Mann-Whitney U test, and the sample sizes of the two groups: r = 1 – (2U)/(n1 n2). Note that U is defined here according to the classic definition as the smaller of the two U values which can be computed from the data. This ensures that 2U < n1n2, as n1n2 is the maximum value of the U statistics.

text: An example can illustrate the use of the two formulas. Consider a health study of twenty older adults, with ten in the treatment group and ten in the control group; hence, there are ten times ten or 100 pairs. The health program uses diet, exercise, and supplements to improve memory, and memory is measured by a standardized test. A Mann-Whitney U test shows that the adult in the treatment group had the better memory in 70 of the 100 pairs, and the poorer memory in 30 pairs. The Mann-Whitney U is the smaller of 70 and 30, so U = 30. The correlation between memory and treatment performance by the Kerby simple difference formula is r = (70/100) − (30/100) = 0.40. The correlation by the Wendt formula is r = 1 − (2·30)/(10·10) = 0.40.

text: Effect size for ordinal data[edit]

text:
Cliff's delta or

d

{\displaystyle d}

 was originally developed by Norman Cliff for use with ordinal data.[33] In short,

d

{\displaystyle d}

 is a measure of how often one the values in one distribution are larger than the values in a second distribution. Crucially, it does not require any assumptions about the shape or spread of the two distributions.

text:
The sample estimate

d

{\displaystyle d}

 is given by:

text:
d
=

#
(

x

i

>

x

j

)
−
#
(

x

i

<

x

j

)

m
n

{\displaystyle d={\frac {\#(x_{i}>x_{j})-\#(x_{i}<x_{j})}{mn}}}

text:
where the two distributions are of size

n

{\displaystyle n}

 and

m

{\displaystyle m}

 with items

x

i

{\displaystyle x_{i}}

 and

x

j

{\displaystyle x_{j}}

, respectively, and

#

{\displaystyle \#}

 is defined as the number of times.

text:
d

{\displaystyle d}

 is linearly related to the Mann–Whitney U statistic, however it captures the direction of the difference in its sign. Given the Mann–Whitney

U

{\displaystyle U}

,

d

{\displaystyle d}

 is:

text:
The R package orddom calculates

d

{\displaystyle d}

 as well as bootstrap confidence intervals.

text: Confidence intervals by means of noncentrality parameters[edit]

text:
Confidence intervals of standardized effect sizes, especially Cohen's

d

{\displaystyle {d}}

 and

f

2

{\displaystyle {f}^{2}}

, rely on the calculation of confidence intervals of noncentrality parameters (ncp). A common approach to construct the confidence interval of ncp is to find the critical ncp values to fit the observed statistic to tail quantiles α/2 and (1 − α/2). The SAS and R-package MBESS provides functions to find critical values of ncp.

text: t-test for mean difference of single group or two related groups[edit]

text: For a single group, M denotes the sample mean, μ the population mean, SD the sample's standard deviation, σ the population's standard deviation, and n is the sample size of the group. The t value is used to test the hypothesis on the difference between the mean and a baseline μbaseline. Usually, μbaseline is zero. In the case of two related groups, the single group is constructed by the differences in pair of samples, while SD and σ denote the sample's and population's standard deviations of differences rather than within original two groups.

text: and Cohen's

text: is the point estimate of

text: So,

text: t-test for mean difference between two independent groups[edit]

text: n1 or n2 are the respective sample sizes.

text: wherein

text: and Cohen's

text: So,

text: One-way ANOVA test for mean difference across multiple independent groups[edit]

text:
One-way ANOVA test applies noncentral F distribution. While with a given population standard deviation

σ

{\displaystyle \sigma }

, the same test question applies noncentral chi-squared distribution.

text: For each j-th sample within i-th group Xi,j, denote

text: While,

text:
So, both ncp(s) of F and

χ

2

{\displaystyle \chi ^{2}}

 equate

text:
In case of

n
:=

n

1

=

n

2

=
⋯
=

n

K

{\displaystyle n:=n_{1}=n_{2}=\cdots =n_{K}}

 for K independent groups of same size, the total sample size is N := n·K.

text:
The t-test for a pair of independent groups is a special case of one-way ANOVA. Note that the noncentrality parameter

n
c

p

F

{\displaystyle ncp_{F}}

 of F is not comparable to the noncentrality parameter

n
c

p

t

{\displaystyle ncp_{t}}

 of the corresponding t. Actually,

n
c

p

F

=
n
c

p

t

2

{\displaystyle ncp_{F}=ncp_{t}^{2}}

, and

f
~

=

|

d
~

2

|

{\displaystyle {\tilde {f}}=\left|{\frac {\tilde {d}}{2}}\right|}

.

text: Effect sizes descriptors[edit]

text: Whether an effect size should be interpreted small, medium, or large depends on its substantive context and its operational definition. Cohen's conventional criteria small, medium, or big[7] are near ubiquitous across many fields, although Cohen[7] cautioned:

text: "The terms 'small,' 'medium,' and 'large' are relative, not only to each other, but to the area of behavioral science or even more particularly to the specific content and research method being employed in any given investigation....In the face of this relativity, there is a certain risk inherent in offering conventional operational definitions for these terms for use in power analysis in as diverse a field of inquiry as behavioral science. This risk is nevertheless accepted in the belief that more is to be gained than lost by supplying a common conventional frame of reference which is recommended for use only when no better basis for estimating the ES index is available." (p. 25)

text: In the two sample layout, Sawilowsky [16] concluded "Based on current research findings in the applied literature, it seems appropriate to revise the rules of thumb for effect sizes," keeping in mind Cohen's cautions, and expanded the descriptions to include very small, very large, and huge. The same de facto standards could be developed for other layouts.

text: Lenth [34] noted for a "medium" effect size, "you'll choose the same n regardless of the accuracy or reliability of your instrument, or the narrowness or diversity of your subjects. Clearly, important considerations are being ignored here. Researchers should interpret the substantive significance of their results by grounding them in a meaningful context or by quantifying their contribution to knowledge, and Cohen's effect size descriptions can be helpful as a starting point."[4] Similarly, a U.S. Dept of Education sponsored report said "The widespread indiscriminate use of Cohen’s generic small, medium, and large effect size values to characterize effect sizes in domains to which his normative values do not apply is thus likewise inappropriate and misleading."[35]

text: They suggested that "appropriate norms are those based on distributions of effect sizes for comparable outcome measures from comparable interventions targeted on comparable samples." Thus if a study in a field where most interventions are tiny yielded a small effect (by Cohen's criteria), these new criteria would call it "large". In a related point, see Abelson's paradox and Sawilowsky's paradox [36].