In a Study to Investigate the Effects of Regular Exercise

Multiple Choice

In a study to investigate the effects of regular exercise on raising high-density lipoprotein (HDL) cholesterol levels ("good cholesterol") , a random sample of five male subjects known to have low HDL levels had their HDL measured at the beginning of the study and then again after six months on a regular exercise schedule. The data are given in the following table: $$\begin{array} { | l | l | l | l | l | l | } \hline \text { Subject } & 1 & 2 & 3 & 4 & 5 \\\hline \text { Initial HDL } & 31 & 36 & 32 & 28 & 37 \\\hline \text { HDL after 6 months } & 39 & 32 & 44 & 34 & 39 \\\hline \text { Difference } & 8 & - 4 & 12 & 6 & 2 \\\hline\end{array}$$
The data are to be analyzed using the Wilcoxon signed rank test. If the responses have a continuous distribution that is not affected by the different treatments, what is the mean of W⁺?

A) 6
B) 7.5
C) 13
D) 27.5