Elementary Statistics (12th Edition)

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

Chapter 5 - Discrete Probability Distributions - 5-4 Parameters for Binomial Distributions - Basic Skills and Concepts - Page 226: 12


a) Mean:14. Standard deviation:3.47. b)It is not unusually low. Also, the rate can be correct.

Work Step by Step

a) Mean=$n\cdot p=100 \cdot 0.14=14$. Standard deviation: $\sqrt{n \cdot p \cdot (1-p)}=\sqrt{100 \cdot 0.14 \cdot 0.86}=3.47.$ b) If a value is unusual, then it is more than two standard deviations far from the mean. $Minimum \ usual \ value=mean-2\cdot(standard \ deviation)=14-2\cdot3.47=7.06$ $Maximum \ usual \ value=mean+2\cdot(standard \ deviation)=14-2\cdot3.47=20.94$. 8 is between these two values, therefore it is not unusually low. Therefore the rate can be correct.
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