Learning Materials
Features
Discover
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.
Over 30 million students worldwide already upgrade their learning with 91影视!
All the tools & learning materials you need for study success - in one app.
Get started for free
Headache relief Doctors identify 鈥渃hronic tension- type headaches鈥� 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.
Systematic random sample Sample surveys often use a systematic random sample to choose a sample of apartments in a large building or housing units in a block at the last stage of a multistage sample. Here is a description of how to choose a systematic random sample. Suppose that we must choose addresses out of Because we can think of the list as four lists of addresses. Choose of the first addresses at random using Table D. The sample contains this address and the addresses and places down the list from it. If the table gives for example, then the systematic random sample consists of the addresses numbered and
(a) Use Table D to choose a systematic random sample of addresses from a list of Enter the table at line
(b) Like an SRS, a systematic random sample gives all individuals the same chance to be chosen. Explain why this is true. Then explain carefully why a systematic sample is not an SRS.
Comparing cancer treatments The progress of a type of cancer differs in women and men. Researchers want to design an experiment to compare three therapies for this cancer. They recruit male and female patients who are willing to serve as subjects.
(a) Which are the blocks in this experiment: the cancer therapies or the two sexes? Why?
(b) What are the advantages of a randomized block design over a completely randomized design using these subjects?
(c) Suppose the researchers had male and no female subjects available for the study. What advantage would this offer? What disadvantage?
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.
Seed weights Biological measurements on the same species often follow a Normal distribution quite closely. The weights of seeds of a variety of winged beans are approximately Normal with a mean of milligrams (mg) and a standard deviation of 110 mg.
(a) What percent of seeds weigh more than mg? Show your method.
(b) If we discard the lightest of these seeds, what is the smallest weight among the remaining seeds? Show your method.
What do you think about this solution?
We value your feedback to improve our textbook solutions.
Explanations 
Textbooks 
Flashcards 
91影视 AI 
Notes 
Study Plans 
Study Sets 
Find a degree 
Magazine