Statistics: Informed Decisions Using Data (4th Edition)

Published by Pearson
ISBN 10: 0321757270
ISBN 13: 978-0-32175-727-2

Chapter 7 - Review - Review Exercises - Page 394: 13b

Answer

$P(125)=0.0213$

Work Step by Step

$μ_X=np=250\times0.46=115$ $σ_X=\sqrt {np(1-p)}=\sqrt {250\times0.46(1-0.46)}=7.88$ Let's find the z-scores for 124.5 and 125.5: $z=\frac{X-μ}{σ}=\frac{124.5-115}{7.88}=1.21$ $z=\frac{X-μ}{σ}=\frac{125.5-115}{7.88}=1.33$ According to Table V, the area to the left of the standard normal curve for a z-score equal to 1.21 is 0.8869. According to Table V, the area to the left of the standard normal curve for a z-score equal to 1.33 is 0.9082. The area of the standard normal curve between the z-scores 1.21 and 1.33 is the difference between the area to the left of the standard normal curve for a z-score equal to 1.33 and the area to the left of the standard normal curve for a z-score equal to 1.21: $0.9082-0.8869=0.0213$
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