Dependent samples: the freshman 15

The freshman 15 refers to the urban legend that students gain an average of 15 pounds during their freshman year of college. The weights of 100 freshmen at a certain University were observed in August and then re-examined in May. The claim that the mean difference is equal to 15 pounds is tested at a 0.05 significance level. The result is “fail to reject the null hypothesis”.

What do the results suggest?

What factors could have affected the results?

How can these results be used to make changes on campus?

Please ensure math calculations are included in answer