Elementary Statistics (12th Edition)

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

Chapter 4 - Probability - 4-2 Basic Concepts of Probability - Beyond the Basics - Page 149: 47


relative risk:0.939. ratio of odds:0.940.

Work Step by Step

$p_{t}$ is the proportion of headaches in the treatment group, hence: $p_{t}=\frac{26}{2103}=0.0124.$ $p_{c}$ is the proportion of headaches in the control group, hence: $p_{c}=\frac{22}{1671}=0.0132.$ The relative risk is the ratio of $p_t$ and $p_c$, hence relative risk=$\frac{p_t}{p_c}=\frac{0.0124}{0.0132}=0.939.$ ratio of odds=$\frac{p_t\cdot(1-p_t)}{p_c\cdot(1-p_c)}=\frac{0.0124\cdot(1-0.0124)}{0.0132\cdot(1-0.0132)}=0.940.$
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