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 a0.01 significance level, is there sufficient evidence to support the claim that the drug is effective in lowering systolic blood pressure?
Before 
210 
188 
175 
157 
175 
164 
155 
189 
188 
205 
159 
167 


After 
179 
179 
162 
152 
188 
148 
176 
155 
147 
143 
163 
177 
In this example, μd is the mean value of the differences d for the population of all pairs of data, where each individual difference d is defined as the systolic blood pressure reading before the drug was taken minus the reading after the drug was taken. What are the null and alternative hypotheses for the hypothesis test? What is the T statistic? What is the Pvalue? What is the conclusion?
H0:Null Hypothesis: ( the drug is not effective in lowering systolic blood pressure )
HA; Alternative Hypothesis: ( the drug is effective in lowering systolic blood pressure ) (Claim)
From the given data, values of d = Before  After are got as follows:
d = Before  After = 31, 9, 13, 5,  13, 16,  21, 34, 41, 62,  4,10
From d values, the following statistics are calculated:
n =12
= 13.583
s_{d} = 24.652
test statistic is given by:
df = 12  1 = 11
One Tail  Right Side Test
By Technology, P  value = 0.0414
Since P  value = 0.0414 is greater than = 0.01, the difference is not significant. Fail to reject null hypothesis.
The data do not support the claim that the drug is effective in lowering systolic blood pressure.
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