Question

A simple random sample with n=56 provided a sample mean of 23.5 and a sample standard...

A simple random sample with n=56 provided a sample mean of 23.5 and a sample standard deviation of 4.5.

a. Develop a 90% confidence interval for the population mean (to 1 decimal).

(_____, ______)

b. Develop a 95% confidence interval for the population mean (to 1 decimal).

(_____, ______)

c. Develop a 99% confidence interval for the population mean (to 1 decimal).

(_____, ______)

d. What happens to the margin of error and the confidence interval as the confidence level is increased?

Homework Answers

Answer #1

Solution :

a.

t /2,df = 1.673

Margin of error = E = t/2,df * (s /n)

= 1.673 * (4.5 / 56)

Margin of error = E = 1.0

The 90% confidence interval estimate of the population mean is,

- E < < + E

23.5 - 1.0 < < 23.5 + 1.0

22.5 < < 24.5

A 90% confidence interval for the population mean : (22.5 , 24.5)

b.

t /2,df = 2.004

Margin of error = E = t/2,df * (s /n)

= 2.004 * (4.5 / 56)

Margin of error = E = 1.2

The 95% confidence interval estimate of the population mean is,

- E < < + E

23.5 - 1.2 < < 23.5 + 1.2

22.3 < < 24.7

A 95% confidence interval for the population mean : (22.3,24.7)

c.

t /2,df = 2.668

Margin of error = E = t/2,df * (s /n)

= 2.668 * (4.5 / 56)

Margin of error = E =  1.6

The 99% confidence interval estimate of the population mean is,

- E < < + E

23.5 - 1.6 < < 23.5 + 1.6

21.9 < < 25.1

A 99% confidence interval for the population mean :(21.9 , 25.1)

d.

Margin of error and the confidence interval also increased

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