a doctor would like to estimate the mean difference in the number of hours of sleep for seniors in high school and seniors in college. to do so, he selects a random sample of 50 high school seniors from all high schools in his county. he also selects a random sample of 50 seniors from the colleges in his county. he would like to construct a 95% confidence interval for the true mean difference in the number of hours of sleep for seniors in high school and seniors in college. are the conditions for inference met?