Chapter 4: Q T4.2. (page 274)
You want to take a simple random sample (SRS) of of the students who live in a dormitory on campus. You label the students 001 to 816 in alphabetical order. In the table of random digits, you read the entries.
The first three students in your sample have labels
The correct option is (e)
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Eat well and exercise Most American adolescents don’t eat well and don’t exercise enough. Can middle schools increase physical activity among their students? Can they persuade students to eat
better? Investigators designed a “physical activity intervention” to increase activity in physical education classes and during leisure periods throughout the school day. They also designed a “nutrition intervention” that improved school lunches and offered ideas for healthy home-packed lunches. Each participating school was randomly assigned to one of the interventions, both interventions, or no intervention. The investigators observed physical activity and lunchtime
consumption of fat.
Seat belt uses A study in El Paso, Texas, looked at seat belt use by drivers. Drivers were observed at randomly chosen convenience stores. After they left their cars, they were invited to answer questions that included questions about seat belt use. In all, 75% said they always used seat belts, yet only 61.5% were wearing seat belts when they pulled into the store parking lots.16 Explain the reason for the bias observed in responses to the survey. Do you expect bias in the same direction in most surveys about seat belt use?
Random digits Which of the following statements are true of a table of random digits, and which are false? Briefly explain your answers.
(a) There are exactly four in each row of digits.
(b) Each pair of digits has a chance of being
(c) The digits can never appear as a group
because this pattern is not random.
Headache relief Doctors identify “chronic tension- type headaches” as headaches that occur almost daily for at least six months. Can antidepressant medications or stress management training reduce the number and severity of these headaches? Are both together more effective than either alone? Investigators compared four treatments: antidepressant alone, placebo alone, antidepressant plus stress management, and placebo plus stress management. The headache sufferers named in the following table have agreed to participate in the study.
(a) Outline the design of the experiment. What is this type of design called?
(b) Explain how you would randomly assign the subjects to the four treatment groups. Then carry out your random assignment.
High-speed Internet Laying fiber-optic cable is expensive. Cable companies want to make sure that, if they extend their lines out to less dense suburban
or rural areas, there will be sufficient demand and the work will be cost-effective. They decide to conduct a survey to determine the proportion of households in a rural subdivision that would buy the service. They select a sample of 5 blocks in the subdivision and survey each family that lives on those blocks.
(a) What is the name for this kind of sampling method?
(b) Suppose there are 65 blocks in the subdivision. Use technology or Table D to select 5 blocks to be sampled. Explain your method clearly.
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