When subjects were treated with a drug, their systolic blood pressure readings (

Question

When subjects were treated with a drug, their systolic blood pressure readings (in mm Hg) were measured before and after the drug was taken. Results are given in the table below. Assume that the paired sample data is a simple random sample and that the differences have a distribution that is approximately normal. Using a 0.05 significance level, is there sufficient evidence to support the claim that the drug is effective in lowering systolic blood pressure.

Before

188

210

157

205

189

195

155

164

179

169

158

167

After

179

179

152

143

155

176

156

148

147

186

159

177

Before

Explanation / Answer

From information given, dbar=14.92, sd=22.22, n=12 pairs

Perform paired t test.

SE(dbar)=sd/sqrt n, where sd is standard deviation of difference of systlic blood pressure, n is sample size.

=22.22/sqrt 12

=6.414

t11=(dbar-0)/SE(dbar)

=(14.92-0)/6.414

=2.33

The p value at df=11, alpha=0.05 is 0.040.

The p value is less than alpha=0.05. Therefore, reject null hypothesis (H0:mud=0) to conclude that new drug has been effective enough in lowering systolic blood pressure.

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