A class survey in a large class for first-year college students asked, “about how many hours do you study during a typical week?” the mean response of the 463 students was 13.7 hours. suppose that we know that the study time follows a normal distribution with standard deviation of 7.4 hours in the population of all first-year students at this university. A) use the survey result to give a 99% confidence interval for the mean study time of all first year students. B) what condition not yet mentioned must be met for your confidence interval to be valid?