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Answer:
The 95% confidence interval for the mean savings is ($60.54, $81.46).
Step-by-step explanation:
As there is no information about the population standard deviation of savings and the sample is not large, i.e. <em>n</em> = 20 < 30, we will use a <em>t</em>-confidence interval.
The (1 - <em>α</em>)% confidence interval for population mean (<em>μ</em>) is:
For the data provided compute the sample mean and standard deviation as follows:
The critical value of <em>t</em> for <em>α</em> = 0.05 and (n - 1) = 19 degrees of freedom is:
*Use a <em>t</em>-table for the value.
Compute the 95% confidence interval for the mean savings as follows:
Thus, the 95% confidence interval for the mean savings is ($60.54, $81.46).