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A national vital statistics report indicated that about \(3 \%\) of all births produced twins. Is the rate of twin births the same among very young mothers? Data from a large city hospital found that only 7 sets of twins were born to 469 teenage girls. Test an appropriate hypothesis and state your conclusion. Be sure the appropriate assumptions and conditions are satisfied before you proceed.

Football 2016 During the first 15 weeks of the 2016 season, the home team won 137 of the 238 regular-season National Football League games. Is this strong evidence of a home field advantage in professional football? Test an appropriate hypothesis and state your conclusion. Be sure the appropriate assumptions and conditions are satisfied before you proceed.

WebZine A magazine is considering the launch of an online edition. The magazine plans to go ahead only if it's convinced that more than \(25 \%\) of current readers would subscribe. The magazine contacted a Simple Random Sample of 500 current subscribers, and 137 of those surveyed expressed interest. What should the company do? Test an appropriate hypothesis and state your conclusion. Be sure the appropriate assumptions and conditions are satisfied before you proceed.

Seeds A garden center wants to store leftover packets of vegetable seeds for sale the following spring, but the center is concerned that the seeds may not germinate at the same rate a year later. The manager finds a packet of last year's green bean seeds and plants them as a test. Although the packet claims a germination rate of \(92 \%\), only 171 of 200 test seeds sprout. Is this evidence that the seeds have lost viability during a year in storage? Test an appropriate hypothesis and state your conclusion. Be sure the appropriate assumptions and conditions are satisfied before you proceed.

Women executives A company is criticized because only 13 of 43 people in executive-level positions are women. The company explains that although this proportion is lower than it might wish, it's not a surprising value given that only \(40 \%\) of all its employees are women. What do you think? Test an appropriate hypothesis and state your conclusion. Be sure the appropriate assumptions and conditions are satisfied before you proceed.

Dropouts 2014 Some people are concerned that new tougher standards and high- stakes tests adopted in many states have driven up the high school dropout rate. The National Center for Education Statistics reported that the high school dropout rate for the year 2014 was \(6.5 \%\). One school district whose dropout rate has always been very close to the national average reports that 130 of their 1782 high school students dropped out last year. Is this evidence that their dropout rate may be increasing? Explain.

An airline's public relations department says that the airline rarely loses passengers' luggage. It further claims that on those occasions when luggage is lost, \(90 \%\) is recovered and delivered to its owner within 24 hours. A consumer group that surveyed a large number of air travelers found that only 103 of 122 people who lost luggage on that airline were reunited with the missing items by the next day. Does this cast doubt on the airline's claim? Explain.

John Wayne Like a lot of other Americans, John Wayne died of cancer. But is there more to this story? In 1955 , Wayne was in Utah shooting the film The Conqueror. Acrosss the state line, in Nevada, the United States military was testing atomic bombs. Radioactive fallout from those tests drifted across the filming location. A total of 46 of the 220 people working on the film eventually died of cancer. Cancer experts estimate that one would expect only about 30 cancer deaths in a group this size. a. Is the death rate among the movie crew unusually high? b. Does this prove that exposure to radiation increases the risk of cancer?

The researcher from Chapter 17 ?, Exercise 39 ? tests whether the mean cholesterol level among those who eat frozen pizza exceeds the value considered to indicate a health risk. She gets a P-value of 0.07. Explain in this context what the " \(7 \%\) " represents.

We saw in Chapter 17 ?, Exercise 56 ? that some students checked 6 bags of Doritos marked with a net weight of 28.3 grams. They carefully weighed the contents of each bag, recording the following weights (in grams): 29.2,28.5,28.7,28.9,29.1,29.5 a. Do these data satisfy the assumptions for inference? Explain. b. Find the mean and standard deviation of the weights. c. Test the hypothesis that the net weight is as claimed.