Question

In a random sample of

1313

microwave​ ovens, the mean repair cost was

​$80.0080.00

and the standard deviation was

​$15.5015.50.

Using the standard normal distribution with the appropriate calculations for a standard deviation that is​ known, assume the population is normally​ distributed, find the margin of error and construct a

9090​%

confidence interval for the population mean

muμ.

A

9090​%

confidence interval using the​ t-distribution was

left parenthesis 72.3 comma 87.7 right parenthesis(72.3,87.7).

Compare the results.

The margin of error of

muμ

is

​(Round to two decimal places as​ needed.)

A

9090​%

confidence interval for

muμ

is left parenthesis nothing comma nothing right parenthesis .

​(Round to one decimal place as​ needed.)

Compare the results. Choose the correct answer below.

A.The confidence interval found using the standard normal distribution is

narrower thannarrower than

the confidence interval found using the​ student's t-distribution.

B.The confidence interval found using the standard normal distribution is

the same asthe same as

the confidence interval found using the​ student's t-distribution.

C.The confidence interval found using the standard normal distribution is

wider thanwider than

the confidence interval found using the​ student's t-distribution.

D.

The confidence interval found using the standard normal distribution has smaller lower and upper confidence interval limits.

Answer 1