Chapter 9: Q.17 (page 547)
Explain in plain language why a significance test that is significant at the 1% level must always be significant at the 5% level. If a test is significant at the 5% level, what can you say about its significance at the 1% level?
It is not known the significance atlevel.
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We hear that listening to Mozart improves students’ performance on tests. Maybe pleasant odors have a similar effect. To test this idea, subjects worked two different but roughly equivalent paper-and-pencil mazes while wearing a mask. The mask was either unscented or carried a floral scent. Each subject used both masks, in a random order. The table below gives the subjects’ times with both masks.
Which type of error is more serious in this case? Justify your answer?
Anemia For the study of Jordanian children in Exercise , the sample mean hemoglobin level was mg/dl and the sample standard deviation was mg/dl.
(a) Calculate the test statistic.
(b) Find the P-value using Table . Then obtain a
more precise P-value from your calculator.
Flu vaccine A drug company has developed a new vaccine for preventing the flu. The company claims that fewer than of adults who use its vaccine will get the flu. To test the claim, researchers give the vaccine to a random sample of adults. Of these, get the flu.
(a) Do these data provide convincing evidence to support the company's claim? Perform an appropriate test to support your answer.
(b) Which kind of mistake - a Type I error or a Type II error-could you have made in (a)? Explain.
(c) From the company's point of view, would a Type I error or Type Il error be more serious? Why?
Taking stock An investor with a stock portfolio worth several hundred thousand dollars sued his broker due to the low returns he got from the portfolio at a time when the stock market did well overall. The investor’s lawyer wants to compare the broker’s performance against the market as a whole. He collects data on the broker’s returns for a random sample ofweeks. Over the -year period that the broker has managed portfolios, stocks in the Standard & Poor’s index gained an average of per month. The Minitab output below displays descriptive statistics for these data, along
with the results of a significance test.
(a) Determine whether there are any outliers. Show your work.
(b) Interpret the P-value in context.
(c) Do these data give convincing evidence to support the lawyer’s case? Carry out a test to help you answer this question.
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