Answer
$\sigma_{\bar X}=1.5$
$n=25$
Work Step by Step
The standard error of the mean is given by $\sigma_{\bar X}=\frac{15}{\sqrt {100}}=1.5$
To double the standard error, we have $\frac{15}{\sqrt n}=3$, so $n=25$
Elementary Statistics: A Step-by-Step Approach with Formula Card 9th Edition
by Bluman, Allan
Published by
McGraw-Hill Education
ISBN 10:
0078136334
ISBN 13:
978-0-07813-633-7
Chapter 6 - The Normal Distribution - 6-3 The Central Limit Theorem - Extending the Concepts - Page 354: 29
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