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Chapter 4: Q 40. (page 230)
When we take a census, we attempt to collect data from
(a) a stratified random sample.
(b) every individual selected in an SRS.
(c) every individual in the population.
(d) a voluntary response sample.
(e) a convenience sample.
The correct option is (c) every individual in the population.
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Effects of TV advertising Figure displays the six treatments for a two-factor experiment on TV advertising. Suppose we have students who are willing to serve as subjects. Describe how you would randomly assign the subjects to the treatments
(a) using slips of paper.
(b) using Table D.
(c) using technology.
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 manager of a sports arena wants to learn more about the financial status of the people who are attending an NBA basketball game. He would like to give a survey to a representative sample of the more than fans in attendance. Ticket prices for the game vary a great deal: seats near the court cost over each, while seats in the top rows of the arena cost each. The arena is divided into numbered sections, from to Each section has rows of seats labeled with letters from A (nearest the court) to (top row
of the arena).
Chocolate and happy babies A University of Helsinki (Finland) study wanted to determine if chocolate consumption during pregnancy had an effect on infant temperament at age of 6 months. Researchers began by asking healthy pregnant women to report their chocolate consumption. Six months after birth, the researchers asked mothers to rate their infants鈥� temperament, including smiling, laughter, and fear. The babies born to women who had been eating chocolate daily during pregnancy were found to be more active and 鈥減ositively reactive鈥濃�攁 measure that the investigators said encompasses traits like smiling and laughter.
(a) Was this an observational study or an experiment? Justify your answer.
(b) What are the explanatory and response variables?
(c) Does this study show that eating chocolate regularly during pregnancy helps produce infants with a good temperament? Explain.
More rain for California? The changing climate will probably bring more rain to California, but we don鈥檛 know whether the additional rain will come during the
winter wet season or extend into the long dry season in spring and summer. Kenwyn Suttle of the University of California at Berkeley and his coworkers carried
out an experiment to study the effects of more rain in either season. They randomly assigned plots of open grassland to three treatments: added water equal to of annual rainfall either during January to March (winter) or during April to June (spring), and no added water (control). Thirty-six circular plots of area square meters were available (see the photo), of which were used for this study. One response variable was total plant biomass, in grams per square meter, produced in a plot over a year.
(a) Outline the design of the experiment. What is this type of design called?
(b) Explain how you would randomly assign the experimental units to the three treatments. Then carry out your random assignment.
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