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Chapter 9: Q.101 (page 592)
You are testing against based on an SRS of observations from a Normal population. What values of the statistic are statistically significant at thelevel?
(a)
(b)
(c)
(d)
(c)
The values of the statistic are statistically significant at the level is (d)
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For the study of Jordanian children in Exercise 4, the sample mean hemoglobin level was 11.3 g/dl and the sample standard deviation was 1.6 g/dl. A significance test yields a P-value of 0.0016.
(a) Interpret the P-value in context.
(b) What conclusion would you make if = 0.05? = 0.01? Justify your answer.
(a) Construct and interpret a 95 % confidence interval for the true proportion p of all first-year students at the university who would identify being well-off as an important personal goal.
(b) Explain what the interval in part (a) tells you about whether the national value holds at this university.
We hear that listening to Mozart improves students鈥� 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鈥� times with both masks.
Do you have ESP? A researcher looking for evidence of extrasensory perception (ESP) tests subjects. Four of these subjects do significantly better than random guessing.
(a) Is it proper to conclude that these four people have ESP? Explain your answer.
(b) What should the researcher now do to test whether any of these four subjects have ESP?
People of taste are supposed to prefer fresh-brewed coffee to the instant variety. On the other hand, perhaps many coffee drinkers just want their caffeine fix. A sceptic claims that only half of all coffee drinkers prefer fresh-brewed coffee. To test this claim, we ask a random sample of 50 coffee drinkers in a small city to take part in a study. Each person tastes two unmarked cups-one containing instant coffee and one containing fresh-brewed coffee-and says which he or she prefers. We find that 36 of the 50 choose fresh coffee.
(a) We presented the two cups to each coffee drinker in a random order, so that some people tasted the fresh coffee first, while others drank the instant coffee first. Why do you think we did this?
(b) Do these results give convincing evidence that coffee drinkers favour fresh-brewed over instant coffee? Carry out a significance test to help answer this question.
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