Answer:
a 95% confidence interval for the mean does not include 4 weeks.
Explanation:
The null hypothesis which states that the mean time between haircuts in the population is 4 weeks should be rejected if at 95% confidence interval,the means does not include 4 weeks. That is, that at 95% confidence interval, the probability of a student getting a haircut in 4 weeks is lower than 0.05. It means that the probability of a student getting a haircut in 4 weeks is lower than 5 in 100 cases.