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Chapter 8: Q.8 (page 524)

Suppose we want a 90% confidence interval for the average amount spent on books by freshmen in their first year at a major university. The interval is to have a margin of error of \(2. Based on last year鈥檚 book sales, we estimate that the standard deviation of the amount spent will be close to \)30. The number of observations required is closest to

(a) 25. (b) 30. (c) 608. (d) 609. (e) 865.

Short Answer

Expert verified

The number of observations required is the closest to609.

Step by step solution

01

introduction

We know, confidence level = 90%

Interval is to have a margin of error E=2

The standard deviation of the amount spent will be P =30

02

explanation

Calculating the sample size S=Z2脳P脳QE2

Z=1.645at confidence level =90%

=1.645脳3022=609

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