Elementary Statistics: Picturing the World (6th Edition)

Published by Pearson
ISBN 10: 0321911210
ISBN 13: 978-0-32191-121-6

Chapter 6 - Confidence Intervals - Section 6.1 Confidence Intervals for the Mean - Exercises - Page 306: 29

Answer

n $\approx$ 126

Work Step by Step

1) The z-score corresponding to a 90% Confidence interval is 1.645 2) Substitute z = 1.645, $\sigma$ = 6.8 and E = 1 into the formula: n = $(\frac{z \times \sigma}{E})^{2}$ n = $(\frac{1.645 \times 6.8 }{1})^{2}$ n $\approx$ 125.13 n $\approx$ 126
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