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Chapter 9: Q.10 (page 546)
In planning a study of the birth weights of babies whose mothers did not see a
doctor before delivery, a researcher states the hypotheses as
The problem is incorrect as the population mean value is as per the null hypothesis and is less than as per the alternative hypothesis.
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Charles Darwin, author of On the Origin of Species (1859), designed an experiment to compare the effects of cross-fertilization and self fertilization on the size of plants. He planted pairs of very similar seedling plants, one self-fertilized and one cross-fertilized, in each of potat the same time. After a period of time, Darwin measured the heights (in inches) of all the plants. Here are the data:
(a) Explain why it is not appropriate to perform a paired t test in this setting.
(b) A hasty student generates the Minitab output shown below. What conclusion should he draw at the significance level? Explain
Are TV commercials louder than their surrounding programs? To find out, researchers collected data on randomly selected commercials in a given week. With the television’s volume at a fixed setting, they measured the maximum loudness of each commercial and the maximum loudness in the first seconds of regular programming that followed. Assuming conditions for inference are met, the most appropriate method for answering the question of interest is
(a) a one-proportion z test.
(b) a one-proportion z interval.
(c) a paired t test.
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.
A change is made that should improve student satisfaction with the parking situation at a local high school. Right now, 37% of students approve of the parking that’s provided. The null hypothesis is tested against the alternative.
Asked to explain the meaning of “statistically significant at the A 0.05 level,” a
student says, “This means that the probability that the null hypothesis is true is less than 0.05.” Is this explanation correct? Why or why not?
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