In statistics, sampling bias is a bias in which a sample is collected in such a way that some members of the intended population are less to be included than others. It results in a biased sample, a non-random sample of a population in which all individuals, or instances, were not likely to have been selected. If this is not accounted for, results can be erroneously attributed to the phenomenon under study rather than to the method of sampling. Medical sources sometimes refer to sampling bias as ascertainment bias. Ascertainment bias has the same definition, but is still sometimes classified as a separate type of bias. Sampling bias is classified as a subtype of selection bias, sometimes termed sample selection bias, but some classify it as a separate type of bias. A distinction, albeit not universally accepted, of sampling bias is that it undermines the external validity of a test, while selection bias addresses internal validity for differences or similarities found in the sample at hand. In this sense, errors occurring in the process of gathering the sample or cohort cause sampling bias, while errors in any process thereafter cause selection bias.
However, selection bias and sampling bias are used synonymously. Selection from a specific real area. For example, a survey of high school students to measure teenage use of illegal drugs will be a biased sample because it does not include home-schooled students or dropouts. A sample is biased if certain members are underrepresented or overrepresented relative to others in the population. For example, a "man on the street" interview which selects people who walk by a certain location is going to have an overrepresentation of healthy individuals who are more to be out of the home than individuals with a chronic illness; this may be an extreme form of biased sampling, because certain members of the population are excluded from the sample. Self-selection bias, possible whenever the group of people being studied has any form of control over whether to participate. Participants' decision to participate may be correlated with traits that affect the study, making the participants a non-representative sample.
For example, people who have strong opinions or substantial knowledge may be more willing to spend time answering a survey than those who do not. Another example is online and phone-in polls, which are biased samples because the respondents are self-selected; those individuals who are motivated to respond individuals who have strong opinions, are overrepresented, individuals that are indifferent or apathetic are less to respond. This leads to a polarization of responses with extreme perspectives being given a disproportionate weight in the summary; as a result, these types of polls are regarded as unscientific. Pre-screening of trial participants, or advertising for volunteers within particular groups. For example, a study to "prove" that smoking does not affect fitness might recruit at the local fitness center, but advertise for smokers during the advanced aerobics class, for non-smokers during the weight loss sessions. Exclusion bias results from exclusion of particular groups from the sample, e.g. exclusion of subjects who have migrated into the study area.
Excluding subjects who move out of the study area during follow-up is rather equivalent of dropout or nonresponse, a selection bias in that it rather affects the internal validity of the study. Healthy user bias, when the study population is healthier than the general population. For example, someone in poor health is unlikely to have a job as manual laborer. Berkson's fallacy, when the study population is selected from a hospital and so is less healthy than the general population; this can result in a spurious negative correlation between diseases: a hospital patient without diabetes is more to have another given disease such as cholecystitis, since they must have had some reason to enter the hospital in the first place. Overmatching, matching for an apparent confounder, a result of the exposure; the control group becomes more similar to the cases in regard to exposure than does the general population. Survivorship bias, in which only "surviving" subjects are selected, ignoring those that fell out of view.
For example, using the record of current companies as an indicator of business climate or economy ignores the businesses that failed and no longer exist. Malmquist bias, an effect in observational astronomy which leads to the preferential detection of intrinsically bright objects; the study of medical conditions begins with anecdotal reports. By their nature, such reports only include those referred for treatment. A child who can't function in school is more to be diagnosed with dyslexia than a child who struggles but passes. A child examined for one condition is more to be tested for and diagnosed with other conditions, skewing comorbidity statistics; as certain diagnoses become associated with behavior problems or intellectual disability, parents try to prevent their children from being stigmatized with those diagnoses, introducing further bias. Studies selected from whole populations are showing that many conditions are much more common and much milder than believed. Geneticists are limited in.
As an example, consider a h
Legal education is the education of individuals in the principles and theory of law. It may be undertaken for several reasons, including to provide the knowledge and skills necessary for admission to legal practice in a particular jurisdiction, to provide a greater breadth of knowledge to those working in other professions such as politics or business, to provide current lawyers with advanced training or greater specialisation, or to update lawyers on recent developments in the law. Legal education can take the form of a variety of programs, including: Primary degrees in law, which may be studied at either undergraduate or graduate level depending on the country. Advanced academic degrees in law, such as masters and doctoral degrees. Practice or training courses, which prospective lawyers are required to pass in some countries before they may enter practice. Applied or specialised law accreditation, which are less formal than degree programs but which provide specialised certification in particular areas.
Continuing legal education, which do not lead to a qualification but provide practicing lawyers with updates on recent legal developments. Early Western legal education emerged in Republican Rome; those desiring to be advocates would train in schools of rhetoric. Around the third century BC Tiberius Coruncanius began teaching law as a separate discipline, his public legal instruction had the effect of creating a class of skilled non-priests, a sort of consultancy. After Coruncanius' death, instruction became more formal, with the introduction of books on law beyond the scant official Roman legal texts, it is possible that Coruncanius allowed members of the public and students to attend consultations with citizens in which he provided legal advice. These consultations were held outside the College of Pontiffs, thus accessible to all those interested. Canon and ecclesiastical law were studied in universities in medieval Europe. However, institutions providing education in the domestic law of each country emerged in the eighteen century.
In England, legal education emerged in the late thirteenth century through apprenticeships. The Inns of Court controlled admission to practice and provided some legal training. English universities had taught Roman and canon law for some time, but formal degrees focused on the native common law did not emerge until the 1800s. In many countries, including most of those in the Commonwealth of Nations, the principal law degree is an undergraduate degree known as a Bachelor of Laws. Graduates of such a program are eligible to become lawyers by passing the country's equivalent of a bar exam. In these countries, graduate law programs are advanced degrees which allow for more in-depth study or specialisation. In the United States, the primary law degree is a graduate degree known as the Juris Doctor. Students may pursue such a degree only after completing an undergraduate degree a bachelor's degree; the undergraduate degree can be in any field, though most American lawyers hold bachelor's degrees in the humanities and social sciences.
American law schools are an autonomous entity within a larger university. Primary degrees in law are offered by law schools, known in some countries as faculties of law. Law schools may have varying degrees of autonomy within a particular university or, in some countries, can be independent of any other post-secondary educational institution. Higher degrees allow for more advanced academic study; these include the Masters of Law by coursework or research, doctoral degrees such as the PhD or SJD. Practitioners may undertake a Masters of Law by coursework to obtain greater specialisation in an area in which they practice. In many common law countries, a higher degree in law is common and expected for legal academics. In addition, incorporating practical skills is beneficial for practitioners seeking higher degrees to better prepare them in their respective legal area of practice. In contrast, higher degrees in law are uncommon in the United States within the academy. In some countries, including the United Kingdom, Germany and some states of Australia, the final stages of vocational legal education required to qualify to practice law are carried out outside the university system.
The requirements for qualification as a barrister or as a solicitor are covered in those articles. Legal education providers in some countries offer courses which lead to a certificate or accreditation in applied legal practice or a particular specialisation. Continuing legal education programs are informal seminars or short courses which provide legal practitioners with an opportunity to update their knowledge and skills throughout their legal career. In some jurisdictions, it is mandatory to undertake a certain amount of continuing legal education each year. In Australia most universities offer law as an undergraduate-entry course, or combined degree course; some of these offer a three-year postgraduate Juris Doctor program. Bond University in Queensland runs three full semesters each year, teaching from mid-January to late December; this enables the Bond University Law Faculty to offer the LLB in the usual 8 semesters, but only 22⁄3 years. They offer a JD in two years; the University of Technology, Sydney will from 2010 offer a 2-year accelerated JD program.
In 2008, the University of Melbourne introduced the Melbourne Model, whereby Law is only available as a graduate degree, with students having to have completed a three-year bachelor's degree before being eligible. Students in combined degree programs would spend the first 3 years comple
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
The median is the value separating the higher half from the lower half of a data sample. For a data set, it may be thought of as the "middle" value. For example, in the data set, the median is 6, the fourth largest, the fifth smallest, number in the sample. For a continuous probability distribution, the median is the value such that a number is likely to fall above or below it; the median is a used measure of the properties of a data set in statistics and probability theory. The basic advantage of the median in describing data compared to the mean is that it is not skewed so much by large or small values, so it may give a better idea of a "typical" value. For example, in understanding statistics like household income or assets which vary a mean may be skewed by a small number of high or low values. Median income, for example, may be a better way to suggest; because of this, the median is of central importance in robust statistics, as it is the most resistant statistic, having a breakdown point of 50%: so long as no more than half the data are contaminated, the median will not give an arbitrarily large or small result.
The median of a finite list of numbers can be found by arranging all the numbers from smallest to greatest. If there is an odd number of numbers, the middle one is picked. For example, consider the list of numbers 1, 3, 3, 6, 7, 8, 9This list contains seven numbers; the median is the fourth of them, 6. If there is an number of observations there is no single middle value. For example, in the data set 1, 2, 3, 4, 5, 6, 8, 9the median is the mean of the middle two numbers: this is / 2, 4.5.. The formula used to find the index of the middle number of a data set of n numerically ordered numbers is / 2; this either gives the halfway point between the two middle values. For example, with 14 values, the formula will give an index of 7.5, the median will be taken by averaging the seventh and eighth values. So the median can be represented by the following formula: m e d i a n = a ⌈ # x ÷ 2 ⌉ + a ⌈ # x ÷ 2 + 1 ⌉ 2 One can find the median using the Stem-and-Leaf Plot. There is no accepted standard notation for the median, but some authors represent the median of a variable x either as x͂ or as μ1/2 sometimes M.
In any of these cases, the use of these or other symbols for the median needs to be explicitly defined when they are introduced. The median is used for skewed distributions, which it summarizes differently from the arithmetic mean. Consider the multiset; the median is 2 in this case, it might be seen as a better indication of central tendency than the arithmetic mean of 4. The median is a popular summary statistic used in descriptive statistics, since it is simple to understand and easy to calculate, while giving a measure, more robust in the presence of outlier values than is the mean; the cited empirical relationship between the relative locations of the mean and the median for skewed distributions is, not true. There are, various relationships for the absolute difference between them. With an number of observations no value need be at the value of the median. Nonetheless, the value of the median is uniquely determined with the usual definition. A related concept, in which the outcome is forced to correspond to a member of the sample, is the medoid.
In a population, at most half have values less than the median and at most half have values greater than it. If each group contains less than half the population some of the population is equal to the median. For example, if a < b < c the median of the list is b, and, if a < b < c < d the median of the list is the mean of b and c. Indeed, as it is based on the middle data in a group, it is not necessary to know the value of extreme results in order to calculate a median. For example, in a psychology test investigating the time needed to solve a problem, if a small number of people failed to solve the problem at all in the given time a median can still be calculated; the median can be used as a measure of location when a distribution is skewed, when end-values are not known, or when one requires reduced importance to be attached to outliers, e.g. because they may be measurement errors. A median is only defined on ordered one-dimensional data, is independent of any distance metric. A geometric median, on the other hand, is defined in any number of dimensions.
The median is one of a number of ways
Response rate (survey)
In survey research, response rate known as completion rate or return rate, is the number of people who answered the survey divided by the number of people in the sample. It is expressed in the form of a percentage; the term is used in direct marketing to refer to the number of people who responded to an offer. The general consensus in academic surveys is to choose one of the six definitions summarized by the American Association for Public Opinion Research; these definitions are endorsed by the National Research Council and the Journal of the American Medical Association, among other well recognized institutions. They are: Response Rate 1 – or the minimum response rate, is the number of complete interviews divided by the number of interviews plus the number of non-interviews plus all cases of unknown eligibility. Response Rate 2 – RR1 + counting partial interviews as respondents. Response Rate 3 – estimates what proportion of cases of unknown eligibility is eligible; those respondents estimated to be ineligible are excluded from the denominator.
The method of estimation *must* be explicitly stated with RR3. Response Rate 4 – allocates cases of unknown eligibility as in RR3, but includes partial interviews as respondents as in RR2. Response Rate 5 – is either a special case of RR3 in that it assumes that there are no eligible cases among the cases of unknown eligibility or the rare case in which there are no cases of unknown eligibility. RR5 is only appropriate when it is valid to assume that none of the unknown cases are eligible ones, or when there are no unknown cases. Response Rate 6 – makes that same assumption as RR5 and includes partial interviews as respondents. RR6 represents the maximum response rate; the six AAPOR definitions vary with respect to whether or not the surveys are or completed and how researchers deal with unknown nonrespondents. Definition #1, for example, does NOT include completed surveys in the numerator, while definition #2 does. Definitions 3–6 deal with the unknown eligibility of potential respondents who could not be contacted.
For example, there is no answer at the doors of 10 houses. Maybe 5 of those you know house people who qualify for your survey based on neighbors telling you whom lived there, but the other 5 are unknown. Maybe the dwellers fit your target population, maybe they don't; this may not be considered in your response rate, depending on which definition you use. Example: if 1,000 surveys were sent by mail, 257 were completed and returned the response rate would be 25.7%. A survey’s response rate is the result of dividing the number of people who were interviewed by the total number of people in the sample who were eligible to participate and should have been interviewed. A low response rate can give rise to sampling bias if the nonresponse is unequal among the participants regarding exposure and/or outcome; such bias is known as nonresponse bias. For many years, a survey's response rate was viewed as an important indicator of survey quality. Many observers presumed, but because measuring the relation between nonresponse and the accuracy of a survey statistic is complex and expensive, few rigorously designed studies provided empirical evidence to document the consequences of lower response rates until recently.
Such studies have been conducted in recent years, several conclude that the expense of increasing the response rate is not justified given the difference in survey accuracy. One early example of a finding was reported by Visser, Krosnick and Curtin who showed that surveys with lower response rates yielded more accurate measurements than did surveys with higher response rates. In another study, Keeter et al. compared results of a 5-day survey employing the Pew Research Center’s usual methodology with results from a more rigorous survey conducted over a much longer field period and achieving a higher response rate of 50%. In 77 out of 84 comparisons, the two surveys yielded results that were statistically indistinguishable. Among the items that manifested significant differences across the two surveys, the differences in proportions of people giving a particular answer ranged from 4 percentage points to 8 percentage points. A study by Curtin et al. tested the effect of lower response rates on estimates of the Index of Consumer Sentiment.
They assessed the impact of excluding respondents who refused to cooperate, respondents who required more than five calls to complete the interview, those who required more than two calls. They found no effect of excluding these respondent groups on estimates of the ICS using monthly samples of hundreds of respondents. For yearly estimates, based on thousands of respondents, the exclusion of people who required more calls had a small one. Holbrook et al. assessed whether lower response rates are associated with less unweighted demographic representativeness of a sample. By examining the results of 81 national surveys with response rates varying from 5 percent to 54 percent, they found that surveys with much lower response rates decreased demographic representativeness within the range examined, but not by much. Choung et al. L
American Bar Association
The American Bar Association, founded August 21, 1878, is a voluntary bar association of lawyers and law students, not specific to any jurisdiction in the United States. The ABA's most important stated activities are the setting of academic standards for law schools, the formulation of model ethical codes related to the legal profession; the ABA has 410,000 members. Its national headquarters are in Illinois. C; the ABA was founded on August 21, 1878, in Saratoga Springs, New York, by 75 lawyers from 20 states and the District of Columbia. According to the ABA website, The legal profession as we know it today existed at that time. Lawyers were sole practitioners who trained under a system of apprenticeship. There was no national code of ethics; the purpose of the original organization, as set forth in its first constitution, was "the advancement of the science of jurisprudence, the promotion of the administration of justice and a uniformity of legislation throughout the country...."In 1918 the first women were admitted to the ABA – Judge Mary Belle Grossman of Cleveland and Mary Florence Lathrop of Denver.
The ABA did not allow African-Americans to join until 1943. This discrimination by the ABA led in 1937, of the National Lawyers Guild. Roberta Cooper Ramo was the first female President of the ABA from 1995–1996. In 2016 ABA introduced a new ethics rule prohibiting attorneys from using sexist and condescending terms; the ABA adopts "policy" on certain legislative and national issues, as voted on by its elected, 589-member House of Delegates. Its Board of Governors, with 44 members, has the authority to act for the ABA, consistent with previous action of the House of Delegates, when the House is not in session; the ABA president, elected to a one-year term, is chief executive officer of the association, while the appointed, longer-serving executive director works as chief operating officer. The conclusion of the ABA Annual Meeting, in August, is when a new president takes office, as well as when the main sessions of the House of Delegates take place; the Annual Meeting gives the general membership the opportunity to participate in educational programs and hear speakers address many issues.
In 2010, Jack L. Rives TJAG, was appointed Executive Director and Chief Operating Officer. One function of the ABA is its maintenance of a code of ethical standards for lawyers; the Model Code of Professional Responsibility and/or the newer Model Rules of Professional Conduct have been adopted in 49 states, the District of Columbia and the United States Virgin Islands. The exception is the State Bar of California. According to the ABA, it "provides law school accreditation, continuing legal education, information about the law, programs to assist lawyers and judges in their work, initiatives to improve the legal system for the public; the Mission of the American Bar Association is to be the national representative of the legal profession, serving the public and the profession by promoting justice, professional excellence and respect for the law." Since 1923, law schools which meet ABA standards are listed as "approved". ABA accreditation is important not only because it affects the recognition of the law schools involved, but it affects a graduate's ability to practice law in a particular state.
In most U. S. jurisdictions, graduation from an ABA-accredited law school is prerequisite towards being allowed to sit for that state's bar exam, for existing lawyers to be admitted to the bar of another state upon motion. States which recognize unaccredited schools within their borders will not recognize such schools from other jurisdictions for purposes of bar admission. For law students attending ABA-accredited schools, memberships are available for free. Students attending non-ABA accredited law schools are permitted to join the ABA as associate members. In June 2009, the ABA Journal reported that the ABA had been working "for months" to change its accreditation standard, where accreditation will be the result of what kind of lawyer an ABA law school produces as opposed to "input" measures such as faculty size and physical plant. In 2012 a non-profit organization called Law School Transparency called upon the ABA to provide meaningful statistics regarding the employment prospects and salary information of graduates of ABA accredited institutions.
On October 17, 2011, the ABA announced it was considering penalties, including loss of accreditation for schools that misreported their graduates employment data. Starting with the Class of 2011, ABA-accredited law schools were required to file Standard 509 Information Reports that included a host of data, ranging from LSAT scores of law students to bar passage rates of graduates. Employment information was filed separately to the Section. On December 12, 2011, despite the ongoing controversy surrounding law school accreditation standards and inability of law school graduates to service their educational debt, the ABA approved another law school. In 1995 the United States Department of Justice accused the ABA of violating Section 1 of the Sherman Act in its law school accreditation proceedings; the case was resolved with a consent decree. In 2006, the ABA acknowledged that it paid DOJ a $185,000 fine; the American Bar Association Center for Continuing Legal Education serves as the ce
Washington, D. C. formally the District of Columbia and referred to as Washington or D. C. is the capital of the United States. Founded after the American Revolution as the seat of government of the newly independent country, Washington was named after George Washington, first President of the United States and Founding Father; as the seat of the United States federal government and several international organizations, Washington is an important world political capital. The city is one of the most visited cities in the world, with more than 20 million tourists annually; the signing of the Residence Act on July 16, 1790, approved the creation of a capital district located along the Potomac River on the country's East Coast. The U. S. Constitution provided for a federal district under the exclusive jurisdiction of the U. S. Congress, the District is therefore not a part of any state; the states of Maryland and Virginia each donated land to form the federal district, which included the pre-existing settlements of Georgetown and Alexandria.
The City of Washington was founded in 1791 to serve as the new national capital. In 1846, Congress returned the land ceded by Virginia. Washington had an estimated population of 702,455 as of July 2018, making it the 20th most populous city in the United States. Commuters from the surrounding Maryland and Virginia suburbs raise the city's daytime population to more than one million during the workweek. Washington's metropolitan area, the country's sixth largest, had a 2017 estimated population of 6.2 million residents. All three branches of the U. S. federal government are centered in the District: Congress and the U. S. Supreme Court. Washington is home to many national monuments, museums situated on or around the National Mall; the city hosts 177 foreign embassies as well as the headquarters of many international organizations, trade unions, non-profit, lobbying groups, professional associations, including the World Bank Group, the International Monetary Fund, the Organization of American States, AARP, the National Geographic Society, the Human Rights Campaign, the International Finance Corporation, the American Red Cross.
A locally elected mayor and a 13‑member council have governed the District since 1973. However, Congress may overturn local laws. D. C. residents elect a non-voting, at-large congressional delegate to the House of Representatives, but the District has no representation in the Senate. The District receives three electoral votes in presidential elections as permitted by the Twenty-third Amendment to the United States Constitution, ratified in 1961. Various tribes of the Algonquian-speaking Piscataway people inhabited the lands around the Potomac River when Europeans first visited the area in the early 17th century. One group known as the Nacotchtank maintained settlements around the Anacostia River within the present-day District of Columbia. Conflicts with European colonists and neighboring tribes forced the relocation of the Piscataway people, some of whom established a new settlement in 1699 near Point of Rocks, Maryland. In his Federalist No. 43, published January 23, 1788, James Madison argued that the new federal government would need authority over a national capital to provide for its own maintenance and safety.
Five years earlier, a band of unpaid soldiers besieged Congress while its members were meeting in Philadelphia. Known as the Pennsylvania Mutiny of 1783, the event emphasized the need for the national government not to rely on any state for its own security. Article One, Section Eight, of the Constitution permits the establishment of a "District as may, by cession of particular states, the acceptance of Congress, become the seat of the government of the United States". However, the Constitution does not specify a location for the capital. In what is now known as the Compromise of 1790, Alexander Hamilton, Thomas Jefferson came to an agreement that the federal government would pay each state's remaining Revolutionary War debts in exchange for establishing the new national capital in the southern United States. On July 9, 1790, Congress passed the Residence Act, which approved the creation of a national capital on the Potomac River; the exact location was to be selected by President George Washington, who signed the bill into law on July 16.
Formed from land donated by the states of Maryland and Virginia, the initial shape of the federal district was a square measuring 10 miles on each side, totaling 100 square miles. Two pre-existing settlements were included in the territory: the port of Georgetown, founded in 1751, the city of Alexandria, founded in 1749. During 1791–92, Andrew Ellicott and several assistants, including a free African American astronomer named Benjamin Banneker, surveyed the borders of the federal district and placed boundary stones at every mile point. Many of the stones are still standing. A new federal city was constructed on the north bank of the Potomac, to the east of Georgetown. On September 9, 1791, the three commissioners overseeing the capital's construction named the city in honor of President Washington; the federal district was named Columbia, a poetic name for the United States in use at that time. Congress held its first session in Washington on November 17, 1800. Congress passed the District of Columbia Organic Act of 1801 that organized the District and placed the entire territory under the exclusive control of the federal