A study was conducted to estimate u, the mean number of weekly hours that Select

Question

A study was conducted to estimate u, the mean number of weekly hours that Select one answer. U.S. adults use computers at home. Suppose a random sample of 81 U.S. 10 points 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 o = 3.6 hours. A similar study conducted a year earlier estimated that u, 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), which of the following is an appropriate conclusion? A. O The current study does provide significant evidence that the mean number of weekly hours has changed over the past year, since 8 falls outside the confidence interval. B. O The current study does not provide significant evidence that the mean number of weekly hours has changed over the past year, since 8 falls outside the confidence interval. C. O The current study does provide significant evidence that the mean number of weekly hours has changed over the past year, since 8 falls inside the confidence interval. D. O The current study does not provide significant evidence that the mean number of weekly hours has changed over the past year, since 8 falls inside the confidence interval. E. O You cannot draw a conclusion because the only way to reach a conclusion is to find the p- value of the test.

Explanation / Answer

The previous mean was 8 hours which is included in the confidence interval generated on the basis of current sample data. Hence,

Option D is correct.

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