e 6 1225 points MBasicStat7 16E019 My Notes Ask Your Teache

e 6. + -12.25 points MBasicStat7 16E019 My Notes Ask Your Teacher 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 469 students was X 15.4 hours. Suppose that we know that the study time follows a Normal distribution with standard deviation ?-8.9 hours in the population of all first-year students at this university. 8.9 humns in the pa (a) Use the survey result to give a 99% confidence interval for the mean study time of all first-year students. (Round your answers to once decimal place.) to hours (b) What condition not yet mentioned must be met for your confidence interval to be valid? O We need to know if this sample can be considered an SRS of the population of all first-year students at this university O We need to know if this sample is normally distributed. O We need to know if this population is normally distributed We need to know if this sample was a large portion of the population of all first-year students at this university. You may need to use the appropriate Appendix Table to answer this question.

Solution

a)

Z value for 99% CI = 2.576

Low = 15.4 - 2.576 * 8.9/?469 = 14.3

high =15.4 + 2.576 * 8.9/?469 = 16.5

hence interval is

14.3 to 16.5 hours

b)

Correct option is A