A geographer selects 30 counties from the north and 30 counties from the south, matching the two samples on the basis of urban/rural status (whether the county is inside or outside of a metropolitan area), dominant economic activity (manufacturing, retail, service, etc.), voter pattern in the last presidential election (whether the majority voted for the Republican or Democratic candidate). Focusing on the percentage of registered voters who actually voted in the last presidential election, the researcher obtains the following results: The mean of the distribution of differences (D) between northern counties and southern counties for voter turnout is equal to 4.00%, with an estimate of the standard error of the mean difference (SD) = 2.35%. Assume that you're working at the .05 level of significance.
a. Formulate an appropriate null hypothesis.
b. Calculate t.
c. Identify the critical value.
d. State your conclusion.