The Basic Practice of Statistics 7th Edition

Published by W. H. Freeman
ISBN 10: 146414253X
ISBN 13: 978-1-46414-253-6

Chapter 17 - Tests of Significance: The Basics - Apply Your Knowledge - Page 404: 17.15

Answer

There is enough evidence that the mean percentage is less than 20.

Work Step by Step

The z value is Mean = $\frac{18+19.1+ ... + 23.2+19.4}{20}$ = 18.19 z = $\frac{x-u}{o/\sqrt n}$ = $\frac{18.19-20}{2/\sqrt 20}$ = -4.05 $P \approx 0 $ Thus, there is sufficient evidence to reject the null hypothesis.
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