Exercise 4.37 on page 235 describes a study to investigate which method, a recorded phone call or a flyer, is more effective in persuading voters to vote for a particular candidate. Since in this case, the alternative hypothesis is not specified in a particular direction, the hypotheses are H₀: p_c= p_fvs H_a: p_c‰  p_f. All else is as in Exercise 4.56, including the randomization distribution shown inFigure 4.18.

(a) Sketch smooth curves that roughly approximate the distribution in Figure 4.18 and shade in the proportion of the area corresponding to the p-value for each of D = 0.2 and D = ˆ’0.4.

(b) Two possible sample statistics are given below, along with several possible p-values. Select the most accurate p-value for each sample statistic. 

Statistics : D = 0.2,D = ˆ’0.4

P-values : 0.008, 0.066, 0.150, 0.392, 0.842.

(c) Of all five p-values given in part (b), which provides the strongest evidence that the methods are not equally effective?

Exercise 4.37

When getting voters to support a candidate in an election, is there a difference between a recorded phone call from the candidate or a flyer about the candidate sent through the mail? A sample of 500 voters is randomly divided into two groups of 250 each, with one group getting the phone call and one group getting the flyer. The voters are then contacted to see if they plan to vote for the candidate in question. We wish to see if there is evidence that the proportions of support are different between the two methods of campaigning.

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120 100 80 60 40 20 -0.4 -0.6 -0.2 0.0 0.2 0.4 0.6 Difference Frequency