Elementary Statistics: Picturing the World (6th Edition)

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

Chapter 6 - Confidence Intervals - Section 6.1 Confidence Intervals for the Mean - Exercises - Page 306: 31

Answer

n $\approx$ 7

Work Step by Step

1) The z-score corresponding to an 80% Confidence level is 1.28 2) Substitute z = 1.28, $\sigma$ = 4.1 and E = 2 into the formula: n = $(\frac{z \times \sigma}{E})^{2}$ n = $(\frac{1.28 \times 4.1 }{2})^{2}$ n $\approx$ 6.885 n $\approx$ 7
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