Question 374114
To construct hypotheses, here's one important thing to keep in mind: the null hypothesis always contains an equality (ie an equation). So this rules out choices A and D. So the null hypothesis is {{{H[o]}}}: {{{mu=25}}}



Now because we want to speed up relief, we want the average time to be lower than 25 min. So the alternative hypothesis is {{{H[a]}}}: {{{mu<25}}}



So the answer is B)