A study was conducted in order to estimate p, the mean number of weekly hours that U.S. adults use computers at home. Suppose a random sample of 81 U.S. adults gives a mean weekly computer usage time of 8.5 hours and that from prior studies, the population standard dewation Is assumed to be cr = 3.6 hours. Based on this information, what would be the point estimate for ,u ? [381 C] None of the above. We are 95% confident that the mean number of weekiy hours that U.S. adults use computers at home is: [3 between 8.1 and 8.9. C] between 7.8 and 9.2. C} between 7.7 and 9.3. C] between 7.5 and 9.5. U between 7.3 and 9.7. Which of the following will provide a more informative (i.e., narrower) condence interval than the one in problem 3? C] (A) Using a sample of size 400 (instead of 81). C} (8) Using a sample of size 36 (instead of 81). C] (C) Using a different sample of size 81. C] (D) Using a 90% level of condence (instead of 95%). C] (E) Using a 99% level of confidence (instead of 95%). Cl Both (A) and (D) are correct. How large a sample of U.S. adults is needed in order to estimate u with a 95% confidence interval of length 1.2 hours? Q6 O12 C120 U36 D144