POL221
Methods and Statistics in Political Science
March 25, 2009

Problem Set #3

1. A coin-operated soft drink machine was designed to discharge, on the average, 7 ounces of beverage per cup.  In a test of the machine ten cupfuls of beverage were drawn from the machine and measured.  The mean and standard deviation of the ten measurements were 7.1 ounces and .12 ounce, respectively.  What can we say about the attained significance level for this test, and do these data present sufficient evidence to indicate that the mean discharge differs from 7 ounces?  (In other words, what are the bounds of the p-value, and what does this result say about accepting or rejecting the null hypothesis?)  Does your decision change if α = .10?  Why or why not?

2. The Stata data set media.dta comes from a recent seminar (POL467, Political Manipulation of the News).  Focusing on the issue of the patients' bill of rights, students measured the national media coverage of the White House, the U.S. Senate, and the U.S. House of Representatives.  The codebook for the data set contains more information about the data set.  After reviewing the codebook, access the data set in Stata, and use it to answer the following questions.

   1. Do a single independent-samples difference of means test (or t-test) to examine whether the White House receives coverage similar to that received by congressional institutions (the House and Senate).  You can use Stata to calculate the mean, standard deviation, and number of cases for each variable, but you should conduct the rest of the test by by hand.  Again, make sure that you follow the steps explained in the Ritchey volume.  Assume that the population variances are equal.  (You can use Stata (specifically the independent-samples difference of means test) to check your answers.)

   2. Now consider whether the institutions receive similar levels of coverage in print and broadcast outlets.

      1. Which type of t-test is appropriate for this question?  Make sure that you explain why one test is appropriate, AND why the main alternative test is inappropriate.  How could you recreate the data set to make the main alternative test more appropriate?

      2. Conduct the appropriate test, following the steps outlined in Ritchey.  You can use Stata to calculate all values, instead of doing some by hand.

   You can answer all questions by working together with others, although you should turn in your own individual answers.  You should type your answers, using 1-inch margins and a font no smaller than 10 point.  Hand-drawn or computer-drawn figures can accompany your typed text. This assignment does not have a page limit.  The first page of your paper should still only contain identifying information (your name, etc.).  The text of your answers should begin on the second page (with no identifying information on this or subsequent pages).  Make sure that you include the printout of any calculations in Stata that you use for your answer (only include the relevant calculations; do not turn in all the Stata printout that you produced while figuring out the problem set). The paper should contain appropriate in-text citations for any sources used (including Ritchey and any other sources).  The detailed information for each citation should then appear in a bibliography on a separate page.  The problem set is due at the start of class on April 10.  Papers turned in after 10 minutes after the scheduled start of class will be considered late.  Finally, the Honor Code binds all answers; make sure that you pledge your work.