Astudy was conducted in order to estimate ? , 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 deviation is assumed to be ? = 3.6 hours. based on this information, what would be the point estimate for ) 81(b) 8.5(c) 3.6(d) none of the above. we are 95% confident that the mean number of weekly hours that u. s. adults use computers at home is: (a) between 8.1 and 8.9.(b) between 7.8 and 9.2.(c) between 7.7 and 9.3.(d) between 7.5 and 9.5.(e) between 7.3 and 9.7.which of the following will provide a more informative (i. e., narrower) confidence interval than the one in problem 3? (a) using a sample of size 400 (instead of ) using a sample of size 36 (instead of ) using a different sample of size 81.(d) using a 90% level of confidence (instead of 95%) using a 99% level of confidence (instead of 95%) both (a) and (d) are correct.(g) both (a) and (e) are correct. how large a sample of u. s. adults is needed in order to estimate ? with a 95% confidence interval of length 1.2 hours? (a) 6(b) 12(c) 20(d) 36(e) 144