## Elementary Statistics (12th Edition)

$H_{0}:\sigma_1=sigma_2,$ $H_{a}:\sigma_1\$ is more than $\sigma_2$. :$F=\frac{s_1^2}{s_2^2}=\frac{2.2^2}{0.72^2}=9.336.$ The critical values by the table with df=min(21,21)=21: $f_{0.05}$ is between 2.054 and 2.096. If the value of the test statistic is in the rejection region, reject the null hypothesis. 9.336 is more than 2.096, hence we reject the null hypothesis.