Question

In November 1993, the state of Pennsylvania conducted clections for its state legislature. The result in the Senate election in the 2nd district (based in Philadelphia) was challenged in court and ultimately overturned. The Democratic candidate won 19,127 of the votes cast by voting machine, while the Republican won 19,691 votes cast by voting machine, giving the Republican a lead of 564 votes. However, the Democrat won 1,391 absentee ballots, while the Republican won just 366 absentee ballots, more than offsetting the Republican lead based on the votes recorded by machines on election day. The Republican candidate sued, claiming that many of the absentee ballots were fraudulent. The judge in the case solicited expert analysis from Orley Ashenfelter an economist at Princeton University. Ashenfelter used a regression model to examine the rela- tionship between absentee vote margins and machine vote margins in 21 previous Pennsylvania Senate elections in seven districts in the Philadelphia area over the preceding decade ear 15904 82 84 593 9444 84 1797 84 34 63208 15671 36276 36710 21848 65862 15194 56100 293 86 360 401 829 151 349 26047 92 92 368 45512 92 5700 92 391 LO2与 564 (a) Use JMP to create a scatterplot for the difference in absentee ballots as a function of the difference in voting machine ballots. Explain under which conditions it would make sense to expect a roughly linear relationship between the two variables. Your conditions should be assumptions on the behavior of Philadelphia's voting public. Include your plot in your homework. (b) Use JMP to fit a simple lincar regression model for DIFFERENCEABSENTEE as a function of DIFFERENCEMACHINE for all but the contested elections. Include the output of the analysis in your homework. Include both the ANOVA table as well as the parameter estimates table (c) What percentage of the variation in DIFFERENCEABSENTEE can be explained by margins (Democrat - Republican) for absentee ballots (DIFFERENCEABSENTEE)? d) Find the p-value for the test Ho : Bo-0 in your output. Explain (as you would to the judge in this case) what this ber tells us. Interpret the results of the test in the context of the problem

Answer 1

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