A clinical trial was conducted to test the effectiveness of a drug for treating insomnia in older subjects. Before treatment,
1616
subjects had a mean wake time of
102.0102.0
min. After treatment, the
1616
subjects had a mean wake time of
97.597.5
min and a standard deviation of
20.320.3
min. Assume that the
1616
sample values appear to be from a normally distributed population and construct a
9090%
confidence interval estimate of the mean wake time for a population with drug treatments. What does the result suggest about the mean wake time of
102.0102.0
min before the treatment? Does the drug appear to be effective?
Solution :
degrees of freedom = n - 1 = 16 - 1 = 15
t/2,df = t0.05,15 = 1.753
Margin of error = E = t/2,df * (s /n)
= 1.753 * ( 20.3/ 16)
Margin of error = E = 8.9
The 90% confidence interval estimate of the population mean is,
- E < < + E
97.5 - 8.9 < < 97.5 + 8.9
88.6 < < 106.4
The confidence interval include the mean wake time of 102.0 min.before the treatment so the means before and after the treatment are same this result suggests that the drug treatment does not have a significant effect
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