Level of Confidence, (1

)

100%

Area in Each Tail,

2

Critical Value,

z/2

90%

0.05

1.645

95%

0.025

1.96

99%

0.005

2.575

People were polled on how many books they read the previous year. Initial survey results indicate that s= 13.5 books. Complete parts (a) through (d) below.

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(a) How many subjects are needed to estimate the mean number of books read the previous year within

four books with

95% confidence?

This

95% confidence level requires

44

44 subjects. (Round up to the nearest subject.)

(b) How many subjects are needed to estimate the mean number of books read the previous year within

two books with

95% confidence?

This

95% confidence level requires

176

176 subjects. (Round up to the nearest subject.)

(c) What effect does doubling the required accuracy have on the sample size?

A.

Doubling the required accuracy nearly doubles the sample size.

B.

Doubling the required accuracy nearly quadruples the sample size.

C.

Doubling the required accuracy nearly halves the sample size.

D.

Doubling the required accuracy nearly quarters the sample size.