Question

A study was conducted to estimate μ, 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 σ = 3.6 hours. The 95% confidence interval for the mean, μ, is (7.7, 9.3).

Which of the following will provide a more informative (i.e., narrower) confidence interval than the 95% confidence interval? Check all that apply.

1. Using a sample of size 400 (instead of 81)
2. Using a sample of size 36 (instead of 81)
3. Using a different sample of size 81
4. Using a 90% level of confidence (instead of 95%)
5. Using a 99% level of confidence (instead of 95%)

Answer 1