Elementary Statistics (12th Edition)

Published by Pearson
ISBN 10: 0321836960
ISBN 13: 978-0-32183-696-0

Chapter 7 - Estimates and Sample Sizes - 7-3 Estimating a Population Mean - Basic Skills and Concepts: 29

Answer

110.It isn't right that the standard deviation is estimated, because we have to know the exact value.

Work Step by Step

$\alpha=1-0.98=0.02.$ Using the table: $z_{\alpha/2}=z_{0.01}=2.33.$ Standard deviation=$\frac{range}{4}=\frac{2400-600}{4}=450.$ Hence the sample size:$\left (\frac{z_{\alpha/2}\cdot \sigma}{E}\right)^2=\left (\frac{2.33\cdot450}{100}\right)^2\approx110$.It isn't right that the standard deviation is estimated, because we have to know the exact value.
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