Elementary Statistics (12th Edition)

Published by Pearson
ISBN 10: 0321836960
ISBN 13: 978-0-32183-696-0

Chapter 5 - Discrete Probability Distributions - 5-5 Poisson Probability Distributions - Basic Skills and Concepts: 16

Answer

a)0.0875 b)0.0826

Work Step by Step

a)$P(X=18)=\frac{19.6^{18}\cdot e^{-19.6}}{18!}=0.0875.$ Expected number: $0.0875\cdot40=3.5.$ This is not very close to the actual value. b)$P(X=21)=\frac{19.6^{21}\cdot e^{-19.6}}{21!}=0.0826.$ Expected number: $0.0826\cdot40=3.3.$ This is very close to the actual value.
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