A college library decides that it will block certain web sites from its computers if they are being used too much of the time on ‘recreational’ sites (Facebook, games, etc.). For one day they monitor 36 randomly selected computers and record the number of minutes spent on recreational sites. The sample mean was 149 and the standard deviation was 69. a) Make a 90% confidence interval for the mean number of minutes the library’s computers are used each day for looking at recreational sites. The library had decided that they would invest in software to block certain sites if they had statistically significant evidence that the computers were being used for recreation for more than two hours each day. They’ll do a hypothesis test with H0: μ = 120 and HA: μ > 120 . b) What are the consequences if the test results in a Type I error? Answer in terms of this particular problem, don’t just give or paraphrase the definition of a Type I error. c) Explain how you can use the confidence interval obtained in part a) to predict the outcome of the hypothesis test. d) Perform the hypothesis test.
4. A college library decides that it will block certain web sites from its computers if they are being used too
much of the time on ‘recreational’ sites (Facebook, games, etc.). For one day they monitor 36 randomly
selected computers and record the number of minutes spent on recreational sites. The sample
was 149 and the standard deviation was 69.
a) Make a 90% confidence interval for the mean number of minutes the library’s computers are used each
day for looking at recreational sites.
The library had decided that they would invest in software to block certain sites if they had statistically
significant evidence that the computers were being used for recreation for more than two hours each day.
They’ll do a hypothesis test with H0: μ = 120 and HA: μ > 120 .
b) What are the consequences if the test results in a Type I error? Answer in terms of this particular
problem, don’t just give or paraphrase the definition of a Type I error.
c) Explain how you can use the confidence interval obtained in part a) to predict the outcome of the
hypothesis test.
d) Perform the hypothesis test.
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