Answer:
The confidence interval is (152.03, 159.77)
Step-by-step explanation:
The formula for calculating the confidence interval for a population mean is given by:

The sample size is actually
.
The sample average is
.
Using excel to calculate the standard deviation we get 
The confidence level is
therefore 
We obtain the critical value 
In Excel I calculated the margin error before calculating the confidence interval. The margin error is given by:

Now we can calculate the confidence interval.
