32 Chapter 1 Basic Ideas 14. Longevity: A life insurance company wants to study the life expectancy of people born in 1950. The company’s actuaries examine death certificates of people born in that year to determine how long they lived. 15. Political opinion: A congressman sent out questionnaires to 10,000 constituents to ask their opinions on a new health-care proposal. A total of 200 questionnaires were returned, and 70% of those responding supported the proposal. Write About It 1. Describe the difference between a stratified sample and a cluster sample. 2. Explain why it is better, when possible, to draw a simple random sample rather than a sample of convenience. 3. Describe circumstances under which each of the following samples could be used: simple random sample, a sample of convenience, a stratified sample, a cluster sample, a systematic sample. 4. Suppose that you were asked to collect some information about students in your class for a statistics project. Give some examples of variables you might collect that are: ordinal, nominal, discrete, continuous. 5. Quantitative variables are numerical. Are some qualitative variables numerical as well? If not, explain why not. If so, provide an example. 6. What are the primary differences between a randomized experiment and an observational study? 7. What are the advantages of a double-blind study? Are there any disadvantages? 8. Provide an example of a study, either real or hypothetical, that is conducted by people who have an interest in the outcome. Explain how the results might possibly be misleading. 9. Explain why each of the following questions is leading. Provide a more appropriate wording. a. Should Americans save more money or continue their wasteful spending? b. Do you support more funding for reputable organizations like the Red Cross? Case Study: Air Pollution And Respiratory Symptoms Air pollution is a serious problem in many places. One form of air pollution that is suspected to cause respiratory illness is particulate matter (PM), which consists of tiny particles in the air. Particulate matter can come from many sources, most commonly ash from burning, but also from other sources such as tiny particles of rubber that wear off of automobile and truck tires. The town of Libby, Montana, was recently the focus of a study on the effect of PM on the respiratory health of children. Many houses in Libby are heated by wood stoves, which produce a lot of particulate pollution. The level of PM is greatest in the winter when more stoves are being used, and declines as the weather becomes warmer. The study attempted to determine whether higher levels of PM affect the respiratory health of children. In one part of the study, schoolchildren were given a questionnaire to bring home to their parents. Among other things, the questionnaire asked whether the child had experienced symptoms of wheezing during the past 60 days. Most parents returned the questionnaire within a couple of weeks. Parents who did not respond promptly were sent another copy of the questionnaire through the mail. Many of these parents responded to this mailed version. Table 1.2 presents, for each day, the number of questionnaires that were returned by parents of children who wheezed, the number returned by those who did not wheeze, the average concentration of particulate matter in the atmosphere during the past 60 days (in units of micrograms per cubic meter), and whether the questionnaires were delivered in school or through the mail. We will consider a PM level of 17 or more to be high exposure, and a PM level of less than 17 to be low exposure. 1. How many people had high exposure to PM? 2. How many of the high-exposure people had wheeze symptoms? 3. What percentage of the high-exposure people had wheeze symptoms? 4. How many people had low exposure to PM? 5. How many of the low-exposure people had wheeze symptoms? 6. What percentage of the low-exposure people had wheeze symptoms? 7. Is there a large difference between the percentage of high-exposure people with wheeze and the percentage of low-exposure people with wheeze? 8. Explain why the percentage of high-exposure people with wheeze is the same as the percentage of school-return people with wheeze.
navidi_monk_essential_statistics_1e_ch1_3
To see the actual publication please follow the link above