Final answer:
The null hypothesis is that the mean length of time students spend doing homework each week is equal to or less than 2.5 hours, while the alternative hypothesis is that the mean length of time has increased and is greater than 2.5 hours.
Step-by-step explanation:
To conduct a hypothesis test, we need to define the null and alternative hypotheses. In this case, the null hypothesis, denoted by H0, would state that the mean length of time students spend doing homework each week is equal to or less than 2.5 hours. The alternative hypothesis, denoted by Ha or H1, would state that the mean length of time has increased and is greater than 2.5 hours.