The Internal Revenue Service (IRS) provides a toll-free help line for taxpayers to call in and get answers to questions as they prepare their tax returns. In recent years, the IRS has been inundated with taxpayer calls and has redesigned its phone service as well as posted answers to frequently asked questions on its website (The Cincinnati Enquirer, January 7, 2010). According to a report by a taxpayer advocate, callers using the new system can expect to wait on hold for an unreasonably long time of 12 minutes before being able to talk to an IRS employee. Suppose you select a sample of 50 callers after the new phone service has been implemented; the sample results show a mean waiting time of 10 minutes before an IRS employee comes on the line. Based upon data from past years, you decide it is reasonable to assume that the standard deviation of waiting time is 8 minutes. Using your sample results, can you conclude that the actual mean waiting time turned out to be significantly less than the 12-minute claim made by the taxpayer advocate? Use ex = .05.

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10 years ago

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No, you cannot conclude that the actual mean waiting time is significantly less than the 12-minute claim made by the taxpayer advocate. To do this, you would need to calculate the z-score for the sample mean of 10 minutes and compare it to the z-score for the 12-minute claim. Since the z-score for the sample mean is not greater than the z-score for the 12-minute claim, you cannot reject the null hypothesis that the mean waiting time is 12 minutes.

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The Internal Revenue Service (IRS) provides a toll-free help line for taxpayers to call in and get answers to questions as they prepare their tax returns. In recent years, the IRS has been inundated with taxpayer calls and has redesigned its phone service as well as posted answers to frequently asked questions on its website (The Cincinnati Enquirer, January 7, 2010). According to a report by a taxpayer advocate, callers using the new system can expect to wait on hold for an unreasonably long time of 12 minutes before being able to talk to an IRS employee. Suppose you select a sample of 50 callers after the new phone service has been implemented; the sample results show a mean waiting time of 10 minutes before an IRS employee comes on the line. Based upon data from past years, you decide it is reasonable to assume that the standard deviation of waiting time is 8 minutes. Using your sample results, can you conclude that the actual mean waiting time turned out to be significantly less than the 12-minute claim made by the taxpayer advocate? Use ex = .05.

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No, you cannot conclude that the actual mean waiting time is significantly less than the 12-minute claim made by the taxpayer advocate. To do this, you would need to calculate the z-score for the sample mean of 10 minutes and compare it to the z-score for the 12-minute claim. Since the z-score for the sample mean is not greater than the z-score for the 12-minute claim, you cannot reject the null hypothesis that the mean waiting time is 12 minutes.

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No, you cannot conclude that the actual mean waiting time is significantly less than the 12-minute claim made by the taxpayer advocate. To do this, you would need to calculate the z-score for the sample mean of 10 minutes and compare it to the z-score for the 12-minute claim. Since the z-score for the sample mean is not greater than the z-score for the 12-minute claim, you cannot reject the null hypothesis that the mean waiting time is 12 minutes.