From a sample of 25 graduate students, the mean number of months of work experience prior to entering an MBA program was 33.59. The national standard deviation is known to be 19 months. What is a 90% confidence interval for the population mean?

The 90% confidence interval for the population mean is between 27.34 months and 39.84 months.

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.

The lower end of the interval is the sample mean subtracted by M. So it is 33.59 - 6.25 = 27.34 months

The upper end of the interval is the sample mean added to M. So it is 33.59 + 6.25 = 39.84 months

The 90% confidence interval for the population mean is between 27.34 months and 39.84 months.

the reporter's right

step-by-step explanation:

1/4 = .25 / 25%