In a random sample of 60 computers, the mean repair cost was $150. Assume the population standard deviation is $36. Construct a 95% confidence interval for the population mean.

The 95% confidence interval for the population mean is between $140.89 and $159.11

Step-by-step explanation:

We have that to find our level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Ztable as such z has a pvalue of .

So it is z with a pvalue of , so

Now, find the margin of error M as such

In which is the standard deviation of the population and n is the size of the sample. So

The lower end of the interval is the sample mean subtracted by M. So it is $150 - $9.11 = $140.89

The upper end of the interval is the sample mean added to M. So it is $150 + $9.11 = $159.11

The 95% confidence interval for the population mean is between $140.89 and $159.11