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Chapter 4 Test Review Guide
The test will consist of both multiple choice and open-response questions, and the questions
will be AP style questions. The following is a list of concepts you need to know, along with
sample problems and some suggested book problems for extra practice.
1) Given a situation, be able to identify the explanatory variable (variable that changes),
response variable (variable that measures the outcome of the study), and experimental units
(the smallest collection of individuals to which treatments are applied).
2) Know why we randomly assign treatments in an experiment (to create groups that are
roughly equivalent).
3) Why do we include control groups in experiments? (avoid confounding variables, give us
comparisons)
4) Know which variables are useful to block for and which do not need to be blocked
5) Differentiate between different types of samples (given a situation, determine the sampling
technique that was employed)
6) Be able to use a table of random digits to find a sample
7) What is the benefit of cluster sampling? (it’s easy)
8) Why do we increase sample size? (increase precision of an estimate, decrease random
chance)
9) Understand and discuss the benefit(s) of using a SRS as opposed to a convenience or
voluntary response sample. Discuss bias and direction of bias with convenience and voluntary
response samples. Compare a SRS to a convenience or voluntary response sample.
10) Discuss the importance of replication in an experiment (larger number of subjects increases
our ability to distinguish the effects of the treatment)
11) Describe a design for an experiment (see question #1c on the next page)
Note: Prior material from other chapters is subject to showing up on the exam.
Suggested book problems for extra practice: pg 230 #12, pg 233 #38, pg 259 #51, pg 264 #88,
pg 265 #92
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Sample Problems
1) High blood pressure adds to the workload of the heart and arteries and may increase the risk
of heart attacks. If not treated, this condition can also lead to heart failure, kidney failure, or
stroke. We wish to test the effectiveness of Angiotensin-converting enzyme (ACE) inhibitors as
a treatment for high blood pressure.
a) It is well known that men and women may react differently to common cardiovascular drug
treatments. What sort of experimental design would you choose for this study, and why?
b) Explain why an experiment involving 600 men and 500 women is preferable to one involving
60 men and 50 women.
c) Assume that 600 men and 500 women suffering from high blood pressure are available for
the study. Describe a design for this experiment. Be sure to include a description of how you
assign individuals to the treatment groups.
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2) We wish to draw a sample of 5 without replacement from a population of 50 households.
Suppose the households are numbered 01, 02, . . . , 50, and suppose that the relevant line of
the random number table is:
11362
35692
96237
90842
46843
62719
64049
17823
What are the households selected?
3) A nutritionist wants to study the effect of storage time (6, 12, and 18 months) on the amount
of vitamin C present in freeze dried fruit when stored for these lengths of time. Six fruit packs
were randomly assigned to each of the three storage times. State the explanatory variable,
experimental units, and response variable.
4) For each situation described, determine which sampling technique is being employed:
a) The names of 110 Statistics students at Swift University are written on 110 pieces of
paper, thrown into a hat, and 22 names are picked from the hat at random.
b) Cactus College divides their student population into undergraduate and graduate,
then a sample is chosen from each group
c) Super Awesome University wants to find out what freshmen think about the food
served on campus. The University has 10 freshmen dorms. They select two dorms at
random and then contact everyone in the selected dorms.