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.

(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 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____subjects. (Round up to the nearest subject.)