Statistics: Informed Decisions Using Data (4th Edition)

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

Chapter 7 - Section 7.4 - Assess Your Understanding - Applying the Concepts - Page 393: 27a

Answer

$P(X\geq75)=0.0007$

Work Step by Step

37% = 0.37 $μ_X=np=150\times0.37=55.5$ $σ_X=\sqrt {np(1-p)}=\sqrt {150\times0.37(1-0.37)}=5.91$ Let's find the z-score for 74.5: $z=\frac{X-μ}{σ}=\frac{74.5-55.5}{5.91}=3.21$ According to Table V, the area of the standard normal curve to the left of the z-score equal to 3.21 is 0.9993. But, we want the area of the standard normal curve to the right (at least 75) of the z-score equal to 0.9993: $1-0.9993=0.0007$
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