Elementary Statistics: A Step-by-Step Approach with Formula Card 9th Edition

Published by McGraw-Hill Education
ISBN 10: 0078136334
ISBN 13: 978-0-07813-633-7

Chapter 6 - The Normal Distribution - Chapter Quiz - Page 365: 32

Answer

$0.0497$

Work Step by Step

Given $p=0.53,q=1−p=0.47,n=250, check np=132.5>5,nq=117.5>5$, we can use a normal distribution approximation to the problem with $\mu=np=132.5,\sigma=\sqrt {npq}=7.891$ For $X<120$ in a binomial distribution, we use $X<119.5$ in the normal approximation, and $z=\frac{119.5-132.5}{7.891}=-1.6474$ thus $P(X<119.5)=P(z)=0.0497$
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