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?

Television viewing reached a new high when the global information and measurement company reported a mean daily viewing time of 8.35 hours per household. use a normal probability distribution with a standard deviation of 2.5 hours to answer the following questions about daily television viewing per household. a. what is the probability that a household views television between 4 and 10 hours a day? (to 4 decimals) b. how many hours of television viewing must a household have in order to be in the top 7% of all television viewing household? (to 2 decimals) c. what is the probability that a household views television more than 4 hours a day? (to 4 decimals)