question 12

In a random sample of 26 people, the mean commute time to work was 34.9 minutes and the standard deviation was 7.3 minutes. Assume the population is normally distributed and use at-distribution to construct a 80% confidence interval for the population mean . What is the margin of error of ? Interpret the results.

The confidence interval for the population mean is (____,____)

(Round to one decimal place asneeded.)

The margin of error of is _____

(Round to one decimal place asneeded.)

Interpret the results.

A.

It can be said that 80% of people have a commute time between the bounds of the confidence interval.

B.

With 80% confidence, it can be said that the commute time is between the bounds of the confidence interval.

C.

With 80% confidence, it can be said that the population mean commute time is between the bounds of the confidence interval.

D.

If a large sample of people are taken approximately 80% of them will have commute times between the bounds of the confidence interval.

question 13

People were polled on how many books they read the previous year. How many subjects are needed to estimate the number of books read the previous year within one book with 95% confidence? Initial survey results indicate that =11.3 books.

A 95% confidence level requires _______

subjects.

(Round up to the nearest whole number asneeded.)

question 14

Use technology to construct the confidence intervals for the population variance 2 and the population standard deviation . Assume the sample is taken from a normally distributed population.

c=0.99, s=38, n=19

The confidence interval for the population variance is (____,___)

(Round to two decimal places asneeded.)

The confidence interval for the population standard deviation is (___,____)

(Round to two decimal places asneeded.)

question 15

In a survey of 3324 adults, 1493 say they have started paying bills online in the last year.

Construct a99% confidence interval for the population proportion. Interpret the results.

A99% confidence interval for the population proportion is (___,___)

(Round to three decimal places asneeded.)

Interpret your results. Choose the correct answer below.

A.

The endpoints of the given confidence interval show that adults pay bills online99% of the time.

B.

With99% confidence, it can be said that the population proportion of adults who say they have started paying bills online in the last year is between the endpoints of the given confidence interval.

C.

With99% confidence, it can be said that the sample proportion of adults who say they have started paying bills online in the last year is between the endpoints of the given confidence interval.