1. Construct the confidence interval for the population mean .

C =0.90, x=7.3, =0.8, and n=50

A 90% confidence interval for is (,) (Round to two decimal places asneeded)

2. Construct the confidence interval for the population mean .

C =0.98, x =15.3, =4.0, and n=40

A 98% confidence interval for is (,) (Round to one decimal place asneeded.)

3. Find the minimum sample size n needed to estimate for the given values ofc, , and E.

C =0.98, =6.6, and E=1

Assume that a preliminary sample has at least 30 members.

N = ?(Round up to the nearest wholenumber.)

4. 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 90% confidence? Initial survey results indicate that =14.3 books.

A 90% confidence level requires () subjects.

(Round up to the nearest whole number asneeded.)

5. A doctor wants to estimate the HDL cholesterol of all20- to29-year-old females. How many subjects are needed to estimate the HDL cholesterol within 2 points with 99% confidence assuming =19.1? Suppose the doctor would be content with 90% confidence. How does the decrease in confidence affect the sample sizerequired?

A99% confidence level requires () subjects.

(Round up to the nearest whole number asneeded.)

6. In a survey of 2689 adults, 1409 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.)

7. In a survey of 8000 women, 5431 say they change their nail polish once a week. Construct a

99% confidence interval for the population proportion of women who change their nail polish once a week.

A 99% confidence interval for the population proportion is (,).

(Round to three decimal places asneeded.)

8. A researcher wishes toestimate, with 99% confidence, the population proportion of adults who are confident with theircountry's banking system. His estimate must be accurate within

22% of the population proportion.

(a) No preliminary estimate is available. Find the minimum sample size needed.

(b) Find the minimum sample sizeneeded, using a prior study that found that 36% of the respondents said they are confident with theircountry's banking system.

(c) Compare the results from parts (a) and (b).

(a) What is the minimum sample size needed assuming that no prior information isavailable?

N =?

(Round up to the nearest whole number asneeded.)

9. A researcher wishes toestimate, with 99% confidence, the population proportion of adults who say chocolate is their favorite ice cream flavor. Her estimate must be accurate within 5% of the population proportion.

(a) No preliminary estimate is available. Find the minimum sample size needed.

(b) Find the minimum sample sizeneeded, using a prior study that found that 38% of the respondents said their favorite flavor of ice cream is chocolate.

(c) Compare the results from parts(a) and(b).

(a) What is the minimum sample size needed assuming that no prior information isavailable?

N =?

(Round up to the nearest whole number asneeded.)

10. The table to the right shows the results of a survey in which 2575 adults from CountryA,1106

adults from CountryB, and 1051 adults from Country C were asked if human activity contributes to global warming. Complete parts(a), (b), and(c).

Adults who say that human activity contributes to global warming

CountryA

60%

Country B

87%

Country C

92%

(a) Construct a 95% confidence interval for the proportion of adults from Country A who say human activity contributes to global warming.

(,) (Round to three decimal places asneeded.)

11. The table shows the results of a survey in which separate samples of 400 adults each from theEast, South,Midwest, and West were asked if traffic congestion is a serious problem in their community. Complete parts(a) and(b).

(a) Construct a95% confidence interval for the proportion of adults from the East who say traffic congestion is a serious problem. The95% confidence interval for the proportion of adults from the East who say traffic congestion is a serious problem is (,) (Round to three decimal places asneeded.)

East36%

South 33%

Midwest 27%

West 54%