Use the standard normal distribution or the t-distribution to construct a 99% confidence interval for the population mean. Justify your decision. If neither distribution can be used, explain why. Interpret the results. In a random sample of 13 mortgage institutions, the mean interest rate was 3.59% and the standard deviation was 0.42%. Assume the interest rates are normally distributed.

Select the correct choice below and, if necessary, fill in any answer boxes to complete your choice.

A. The 99% confidence interval is (_____, _____ ).

(Round to two decimal places as needed.)

B.Neither distribution can be used to construct the confidence interval.

In a random sample of 25 people, the mean commute time to work was 30.8 minutes and the standard deviation was7.2 minutes. Assume the population is normally distributed and use a t-distribution to construct a 80% confidence interval for the population mean .

What is the margin of error of ? ______

(Round to one decimal place as needed.)