15.14 More on blood pressure Refer to the previous exercise.

The analysis there did not take into account the size of the change in blood pressure. Show how to do this with the Wilcoxon signed-ranks test.

a. State the hypotheses for that test, for the relevant onesided alternative hypothesis.

b. Construct the sampling distribution for the rank sum of the positive differences when you consider the possible samples that have absolute differences in blood pressure of 20, 25, and 15.

c. Using the sampling distribution from part

b, find and interpret the P-value. (When every difference is positive, or when every difference is negative, this test and the sign test give the same P-value for a given alternative hypothesis.)