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Question

A Consumer Reports Research Center survey of 427 women showed that 29% of them purchase books online

1) Find a 95% confidence interval estimate of the precentage of all women who purchase books online

Answer 1

Step 1:

The total number of women in the survey n :  427.

The probability that women purchase books online : 29 % = 0.29.

Definition of specific confidence interval for a proportion : ,

where is the population proportion.

is the sample proportion.

.

n is the sample size.

is the confidence interval.

Step 2:

For 95% of confidence interval, .

95% of confidence interval for the proportion is

95% of confidence interval for the proportion of all 29 % women purchase books online is .

Solution:

95% of confidence interval for the proportion of all 29 % women purchase books online is .