A study 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:
A. 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. 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. 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. 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. one of the above. The only way to reach a conclusion is by
finding the p-value of the test.