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Chapter 4: Q 39. (page 230)
an SRS of students from your class to ask where they use a computer for the online exercises. You label the students You enter the table
of random digits at this line:
Your SRS contains the students labeled
The correct option is
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Internet telephone calls You can use Voice over Internet Protocol (VoIP) to make long-distance
telephone calls over the Internet. How will the cost affect the use of this service? A university plans an experiment to find out. It will offer the service to all students in one of its dormitories. Some students will pay a low flat rate. Others will pay higher rates at peak periods and very low rates off-peak. The university is interested in the amount and time of use and inthe effect on the congestion of the network.
The effects of day care Does day care help low- income children stay in school and hold good jobs later in life? The Carolina Abecedarian Project (the name suggests the ABCs) has followed a group of children since . Back then, these individuals were all healthy but low-income black infants in Chapel Hill, North Carolina. All the infants received nutritional supplements and help from social workers. Half were also assigned at random to an intensive preschool program.
(a) Explain the purpose of each of the three experimental design principles.
(b) Describe how each of these principles was used in this study.
Running red lights The sample described in Exercise produced a list of licensed drivers. The investigators then chose an SRS of of these drivers to answer questions about their driving habits. One question asked was: “Recalling the last ten traffic lights you drove through, how many of them were red when you entered the intersections?” Of the respondents, admitted that at least one light had been red. A practical problem with this survey is that people may not give truthful answers. What is the likely direction of the bias: do you think more or fewer than of the respondents really ran a red light? Why?
Got deodorant? A group of students wants to perform an experiment to determine whether Brand A or Brand B deodorant lasts longer. One group member
suggests the following design: Recruit student volunteers—male and female. Separate by gender, since male and female bodies might respond
differently to deodorant. Give all the males Brand A deodorant and all the females Brand B. Have each student rate how well the deodorant is still working at the end of the school day on a 0 to 10 scale. Then compare ratings for the two treatments.
(a) Identify any flaws you see in the proposed design for this experiment.
(b) Describe how you would design the experiment. Explain how your design addresses each of the problems you identified in (a).
Effects of binge drinking A common definition of “binge drinking” is or more drinks at one sitting for men and or more for women. An observational study
finds that students who binge drink have lower average GPA than those who don’t. Identify a lurking variable that may be confounded with the effects of binge drinking. Explain how confounding might occur.
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