(6.4)7c.

As part of a water quality survey, you test the water hardness in several randomly selected streams. The results are shown below. Construct a confidence interval for the population variance

2

and the population standard deviation

.

Use a

95%

level of confidence. Assume that the population has a normal distribution.

n=20

s=18

grains per gallon

Question content area bottom

Part 1

What is the confidence interval for the population variance

2?

187.4187.4,691.1691.1

(Round to one decimal place as needed.)

Part 2

Interpret the results. Select the correct choice below and fill in the answer box(es) to find your choice.

(Round to one decimal places as needed.)

A.

With

95%

confidence, it can be said that the population variance is between

187.4187.4

and

691.1691.1.

Your answer is correct.

B.

With

95%

confidence, it can be said that the population variance is less than

enter your response here.

C.

With

5%

confidence, it can be said that the population variance is between

enter your response here

and

enter your response here.

D.

With

5%

confidence, it can be said that the population variance is greater than

enter your response here.

Part 3

What is the confidence interval for the population standard deviation

?

enter your response here,enter your response here

(Round to one decimal place as needed.)