# Question

A recent Gallup poll asked Americans to disclose the number of books they read during the previous year. Initial survey results indicate that s = 16.6 books.

(a) How many subjects are needed to estimate the number of books Americans read the previous year within four books with 95% conﬁdence?

(b) How many subjects are needed to estimate the number of books Americans read the previous year within two books with 95% conﬁdence?

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

(d) How many subjects are needed to estimate the number of books Americans read the previous year within four books with 99% conﬁdence? Compare this result to part (a). How does increasing the level of conﬁdence in the estimate affect sample size? Why is this reasonable?

(a) How many subjects are needed to estimate the number of books Americans read the previous year within four books with 95% conﬁdence?

(b) How many subjects are needed to estimate the number of books Americans read the previous year within two books with 95% conﬁdence?

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

(d) How many subjects are needed to estimate the number of books Americans read the previous year within four books with 99% conﬁdence? Compare this result to part (a). How does increasing the level of conﬁdence in the estimate affect sample size? Why is this reasonable?

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