4.2.1 An Introduction to Trees – Video 1: The Supreme Court

in this lecture we'll see how analytics can be used to predict the outcomes of cases in the United States Supreme Court this seems like a very unconventional use of analytics but in 2002 a group of political science and law academics decided to test if a model can do better than a group of experts at predicting the decisions of the Supreme Court in this case a very interpretable analytics method was used called classification and regression trees the legal system of the United States operates at the state level and at the federal or countrywide level the federal level is necessary to deal with cases beyond the scope of state law like disputes between states and violations of federal laws the federal court is divided into three levels district courts circuit courts and the Supreme Court cases start at the district courts where an initial decision is made about the case the circuit courts hear appeals from the district courts and can change the decision that was made the Supreme Court is the highest level in the American legal system and makes the final decision on cases the Supreme Court of the United States consists of nine judges or justices who are appointed by the president this image shows the nine Supreme Court justices from the time period in 1994 through 2005 this was the longest period of time with the same set of justices in over a hundred and eighty years the people appointed a Supreme Court justices are usually distinguished judges professors of law or state or federal attorneys the Supreme Court of the United States or SCOTUS decides on the most difficult and controversial cases in the United States these cases often involve an interpretation of the Constitution and have significant social political and economic consequences there have been many significant and groundbreaking decisions made by the Supreme Court these are a few notable decisions that were made in 1942 the Supreme Court decided on the Wickard versus filburn case this case recognized the power of the federal government to regulate economic activity philburn was a farmer who was growing wheat for on-farm consumption however the US had established limits on wheat production and filburn was exceeding those limits so even though the extra wheat he was producing was for his own use and he had no intention of selling it he was forced to destroy it in 1973 the Supreme Court decided on the Roe versus Wade case one of the most well known cases to this day they decided to legalize abortion and by doing this prompted a national debate that continues today about the legality of abortion in 2000 the Supreme Court actually decided the outcome of the presidential election the race was so close in the state of Florida that a recount of the ballots was required but the Florida Secretary of State certified that President Bush was the winner before the recount could be completed the case then went to the Supreme Court where it was ruled that all ballots needed to be recounted but since this could not be done before the winner had to be declared President Bush won the state of Florida and thus the presidency a very recent case from 2012 dealt with the Patient Protection and Affordable Care Act commonly called Obamacare which requires most Americans to have health insurance the Supreme Court upheld this requirement since nonprofits voters and anybody interested in long-term planning can benefit from knowing the outcomes of the Supreme Court cases before they happen legal academics and political scientists regularly make predictions of Supreme Court decisions from detailed studies of the cases and individual justices in 2002 Andrew Martin a professor of political science at Washington University in Saint Louis decided to instead predict decisions using a statistical model built from data together with his colleagues he decided to test the model against a panel of experts they wanted to see if an analytical model could outperform the expertise an intuition of a large group of experts Martin used a method called classification and regression trees or cart in this case the outcome is binary will the Supreme Court affirmed the case or reject the case he could have used logistic regression for this but logistic regression models are not easily interpretable the model coefficients in logistic regression indicate the importance and relative effect of variables but do not give a simple explanation of how a decision is made in this lecture we'll discuss the method of cart and a related method called random forests we will then see if these methods can actually outperform experts in predicting the outcome of Supreme Court cases you

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