Answer
374
Work Step by Step
$\alpha=1-0.99=0.10.$ Then, by using the table, the critical value: $z_{\alpha/2}=z_{0.005}=2.58.$
Hence the sample size:$n=\frac{z^2_{\frac{\alpha}{2}}\cdot \sigma^2}{E^2}=\frac{2.58^2\cdot15^2}{2^2}=374.$
Elementary Statistics (12th Edition)
by Triola, Mario F.
Published by
Pearson
ISBN 10:
0321836960
ISBN 13:
978-0-32183-696-0
Chapter 7 - Estimates and Sample Sizes - Review - Chapter Quick Quiz - Page 373: 6
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