Answer:
![26.12\:](https://tex.z-dn.net/?f=26.12%5C%3A%3C%5C%3A%5Cmu%5C%3A%3C%5C%3A31.48)
Step-by-step explanation:
Since the population standard deviation
is unknown, and the sample standard deviation
, must replace it, the
distribution must be used for the confidence interval.
The sample size is n=8.
The degree of freedom is
,
.
With 95% confidence level, the
(significance level) is 5%.
Hence with 7 degrees of freedom,
. (Read from the t-distribution table see attachment)
The 95% confidence interval can be found by using the formula:
.
The sample mean is
hours.
The sample sample standard deviation is
hours.
We now substitute all these values into the formula to obtain:
.
![26.12\:](https://tex.z-dn.net/?f=26.12%5C%3A%3C%5C%3A%5Cmu%5C%3A%3C%5C%3A31.48)
We are 95% confident that the population mean is between 26.12 and 31.48 hours.