Captopril is a drug designed to lower systolic blood pressure. When subjects were treated with this drug, their systolic blood pressure readings (in mm Hg) were measured before and after the drug was taken. Results are given in the accompanying table (based on data from €œEssential Hypertension: Effect of an Oral Inhibitor of Angiotensin-Converting Enzyme,€ by MacGregor et al., British Medical Journal, Vol. 2). Using a 0.01 significance level, is there sufficient evidence to support the claim that Captopril is effective in lowering systolic blood pressure?

Assume that the paired sample data are simple random samples and that the differences have a distribution that is approximately normal.

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SubjectA 8C DEFGHKL Before200 174 198 170 179 182193 209 185 155 169 210 After 9 170 177 167159 151 176 183 159 145 146 177