#10

A publisher wants to estimate the mean length of time (in minutes) all adults spend reading newspapers. To determine this estimate, the publisher takes a random sample of 15 people and obtains the results below. From past studies, the publisher assumes is 1.7 minutes and that the population of times is normally distributed.

8

9

11

10

8

8

8

12

10

6

12

7

11

9

9

Construct the 90% and 99% confidence intervals for the population mean. Which interval is wider? If convenient, use technology to construct the confidence intervals.

The 90% confidence interval is

(_____,_____).(round to one decimal place as needed).

The 99% confidence interval is

(_____,_____).(round to one decimal place as needed).

Which interval is wider?________

________________________________________________________________________________________________________________

# 9

You are given the sample mean and the population standard deviation. Use this information to construct the 90% and 95% confidence intervals for the population mean. Interpret the results and compare the widths of the confidence intervals. If convenient, use technology to construct the confidence intervals. A random sample of 55 home theater systems has a mean price of $126.00. Assume the population standard deviation is $18.70.

The 90% confidence interval is ______,______ (round to two decimal places as needed.)

The 95% confidence interval is _______,_______ (round to two decimal places as needed.)