Elementary Statistics (12th Edition)

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

Chapter 3 - Statistics for Describing, Exploring, and Comparing Data - 3-2 Measures of Center - Beyond the Basics - Page 95: 36


45.3 is the harmonic mean, which represetns the mean speed of the trip.

Work Step by Step

The mean speed is (38+56)/2=47, but the harmonic mean of speed is: $\frac{2}{\frac{1}{38}+\frac{1}{56}}=45.3$, and this is actually the mean speed of the trip because $time=\frac{distance}{speed}$.
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