Question

People were polled on how many books they read the previous year. Initial survey results indicate that sequals 10.9 books. Complete parts ​(a) through ​(d) below.

Answer 1

a)

suppose this is the question

How many subjects are needed to estimate the mean number of books read the previous year within 6 books with 90​%​confidence?

n = z^2* s^2/e^2

now s = 10.9

e = 6 {it could be different number in your case)

z =1.96 for 95% and 1.645 for 90% level and 2.576 for 99%

n = (1.645 * 10.9/6)^2 = 8.93

= 9

b)

if e = 3

then n = (1.645 * 10.9/3)^2 = 35.722

= 36

c)

Doubling the required accuracy nearly quadruples the sample size.

d)

for 99%

e = 6

n = (2.576 * 10.9/6)^2 = 21.899

n = 22

Increasing the level of confidence increases the sample size required. For a fixed margin of​ error, greater confidence can be achieved with a larger sample size.

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