## Elementary Statistics (12th Edition)

$p_{t}$ 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=$\frac{p_t\cdot(1-p_t)}{p_c\cdot(1-p_c)}=\frac{0.0124\cdot(1-0.0124)}{0.0132\cdot(1-0.0132)}=0.940.$