A Weight-Lifting Coach Claims That a Weight-Lifter Can Increase Strength

Essay

A weight-lifting coach claims that a weight-lifter can increase strength by taking vitamin E. To test the theory, the coach randomly selects 9 athletes and gives them a strength test using a bench press. Thirty days later, after regular training supplemented by vitamin E, they are given the same test again. The weights pressed (in pounds) before and after the vitamin E regimen are shown below. Use the Wilcoxon signed rank test to test the claim that the vitamin E supplement is effective in increasing the athletes' strength. Use ? = 0.05. $$\begin{array} { l c c c c c c c c c } \hline \text { Athlete } & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\\hline \text { Before } & 221 & 273 & 216 & 259 & 238 & 227 & 213 & 244 & 239 \\\text { After } & 231 & 278 & 216 & 257 & 245 & 242 & 218 & 239 & 244\end{array}$$