Question

A clinical trial was conducted to test the effectiveness of a drug for treating insomnia in older subjects. Before treatment, 13 subjects had a mean wake time of 101.0 min. After treatment, the 13 subjects had a mean wake time of 94.8 min and a standard deviation of 23.62 min. Assume that the 13 sample values appear to be from a normally distributed population and construct a 95% 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 101.0 min before the treatment? Does the drug appear to be effective?

Answer #1

Solution :

degrees of freedom = n - 1 = 13 - 1 = 12

t/2,df
= t_{0.025,12} = 2.179

Margin of error = E = t_{/2,df}
* (s /n)

= 2.179 * ( 23.62 / 13)

Margin of error = E = 14.3

The 95% confidence interval estimate of the population mean is,

- E < < + E

94.8 - 14.3 < < 94.8 + 14.3

(80.5 min. < < 109.1 min.)

The confidence interval include the mean wake time of 101.0 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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