It is desired to study the effect of a special diet on systolic blood pressure. The following sample data are obtained for eight adults over 40 years of age before and after six months of this diet.

At 95% confidence level, is there evidence to conclude that the new diet reduces the systolic blood pressure in individuals of over 40 years old? Test (a) using the sign test, and (b) using the Wilcoxon signed rank test. Interpret the results.

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Before 185 222 235 198 224 197 228 234 After 188 217 229 190 226 185 225 231