Answer
15 flights lasted between 3 and 7 days
Work Step by Step
Mean = 7
S.D = 2
Mean - 2 S.D = 7 - 4 = 3
Mean + 2 S.D = 7 + 4 = 11
So k= 2
The probability = 0.75
So n = 20 * 0.75 = 15
Elementary Statistics: Picturing the World (6th Edition)
by Larson, Ron; Farber, Betsy
Published by
Pearson
ISBN 10:
0321911210
ISBN 13:
978-0-32191-121-6
Chapter 2 - Descriptive Statistics - Review Exercises - Page 118: 32
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