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# Confidence interval and hypothesis testing.

Captopril is a drug designed to lower systolic blood pressure. When subjects were tested with this drug, their systolic blood pressure readings (in mm of mercury) were measured before and after the drug were taken, with the results given in the table:

a. Construct a 99% confidence interval for the mean difference between the before and after readings.
b. Is there sufficient evidence to support the claim that captopril is effective in lowering systolic blood pressure?

Subject A B C D E F G H I J K L
Before 200 174 198 170 179 182 193 209 185 155 169 210
After 191 170 177 167 159 151 176 183 159 145 146 177

#### Solution Preview

Solution:

Using the Statdisk software we get the results as :

n =12

Difference mean d =18.58333

Difference St Dev, sd =10.10363

Test statistic t = ...

#### Solution Summary

The solution computes 99% confidence intervals for the mean difference. From this, a conclusion whether captopril is effective at lowering systolic blood pressure is shown.

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