Elementary Statistics: A Step-by-Step Approach with Formula Card 9th Edition

Published by McGraw-Hill Education
ISBN 10: 0078136334
ISBN 13: 978-0-07813-633-7

Chapter 8 - Hypothesis Testing - 8-2 z Test for a Mean - Exercises 8-2 - Page 437: 25

Answer

The null hypothesis can be rejected at α=0.05 and this means that the average number of days per year missed by the employees due to illness is less than the national average of 10.

Work Step by Step

Given that, $$μ=10, σ=3.63,n=40, then,\\ \bar x=(0+6+...+1+9)/40=201/40 \approx 5.025,\\ H0:μ\geq10.\\H1:μ \lt 10.\\ Z=\frac{\bar x −μ}{\frac{σ}{\sqrt{n}}} = \frac{5.025−10}{\frac{3.63}{\sqrt{40}}} ≈ -8.67\\ P-value =P(Z\leq -8.67))\approx 0.0000\\$$ Since α=0.05 and P−value=0.0000, the null hypothesis can be rejected.
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