Astudy was conducted in order 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. a similar study conducted a year earlier estimated that μ, the mean number of weekly hours that u. s. adults use computers at home, was 8 hours. we would like to test (at the usual significance level of 5%) whether the current study provides significant evidence that this mean has changed since the previous year. using a 95% confidence interval of (7.7, 9.3), our conclusion is that: