Chapter 4: Q 2.2. (page 240)
Describe how you would carry out the random assignment. Provide enough detail that a classmate could implement your procedure.
Short Answer
All classes are given to candidates at random.
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Chapter 4: Q 2.2. (page 240)
Describe how you would carry out the random assignment. Provide enough detail that a classmate could implement your procedure.
All classes are given to candidates at random.
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Sampling gravestones The local genealogical society in Coles County, Illinois, has compiled records on all gravestones in cemeteries in the county from the years to Historians plan to use these records to learn about African Americans in Coles County鈥檚 history. They first choose an SRS of records to check their accuracy by visiting the actual gravestones.
(a) Explain how you would use technology or Table D to choose the SRS. Your description should be clear enough for a classmate to obtain your results.
(b) Use your method from (a) to choose the first gravestones.
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.

Student archaeologists An archaeological dig turns up large numbers of pottery shards, broken stone tools, and other artifacts. Students working on the project classify each artifact and assign it a number. The counts in different categories are important for understanding the site, so the project director chooses of the artifacts at random and checks the students鈥 work. Identify the population and the sample.
Do placebos really work? Researchers in Japan conducted an experiment on 1 individuals who were extremely allergic to poison ivy. On one arm, each subject was rubbed with a poison ivy leaf and told the leaf was harmless. On the other arm, each subject was rubbed with a harmless leaf and told it was poison ivy. All the subjects developed a rash on the arm where the harmless leaf was rubbed. Of the
subjects, 11 did not have any reaction to the real poison ivy leaf.
(a) What was the placebo in this experiment?
(b) Explain how the results of this study support the idea of a placebo effect.
Does eating dinner with their families improve students鈥 academic performance? According to an ABC News article, 鈥淭eenagers who eat with their families at least five times a week are more likely to get better grades in
school.鈥19 This finding was based on a sample survey conducted by
researchers at Columbia University.
What are the explanatory and response variables?
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