Chapter 5 Practice Questions
Questions on the Vocabulary of Data Collection
1. Which of the following is a characteristic of a census?
A. It's based on anecdotal evidence.
B. It's generally more accurate than a sample.
C. It uses secondary data.
D. It's always part of an experiment.
E. It gathers data from every member of a population.
2. True or False: If a researcher uses a sample to make inferences about a population, the
most important consideration is that the sample be large enough to make generalizations
from it.
3. Which of the following are true?
I. There's always a treatment in an experiment.
II. An observational study is one type of experiment.
III. Sample surveys are experiments.
A. I only
B. II only
C. II and III only
D. I and III only
E. All of these are true
4. A teacher wants to compare the mean GPA of statistics students to mean GPA of all
students at her high school. She looks up the GPAs of the statistics students and finds the
mean. She then compares this mean to the mean GPA of all students. Which of the
following are true?
I. This teacher will be relying on available evidence, or secondary data.
II. This is an observational study.
III. This is an experiment, since there is a comparison of a sample to a population.
A. I only
B. II only
C. III only
D. I and II only
E. II and III only
5. Your good friend Bill tells you that he has proof that not wearing your seat belt is safer
than wearing one. His friend, Darlene, was in a bad accident. She wasn't wearing her seat
belt and was thrown clear of the car. The car immediately burst into flames. Darlene
would have been killed if she hadn't been thrown clear. Which of the following
statements is true?
A. Since Bill is a trusted friend, this is good evidence that seat belts aren't as safe as the
authorities would have you believe.
B. This is a good example of using available evidence to help make a decision.
C. This is an example of anecdotal evidence and shouldn't be used to make a decision
about wearing seat belts.
D. This is an example of an experiment that proves that it may be safer not to wear a seat
belt.
E. This should be considered good evidence for not wearing a seat belt, but you should do
a study to be more confident in your decision before reaching a conclusion.
6. You want to demonstrate that people are influenced by a cola's product name over
product quality. You set up two tables on opposite sides of the quad of your school, so
people can taste a name brand and a store brand cola and tell you which they prefer. At
one table the tasters drink the colas in unmarked cups, so that they don't know which cup
contains which cola. At the other table, the subjects drink each cola from its original can.
You analyze the results and report your findings in the school newspaper.
Which of the following is true:
A. This is an experiment, since you imposed a treatment on some subjects and left others
untreated.
B. This is an observational study, since you merely collected data and made a comparison
based on your data.
C. This is an experiment for which you used available data: students who were willing to
taste the two colas.
D. There was no experimental design, since you didn't decide on treatments or on how
groups would be assigned to treatments.
E. This was not an experiment because your groups weren't selected randomly.
Questions on Data Collection
7. Which of the following is an example of using anecdotal rather than available data to
support a conclusion?
A. Using the results of a nationwide survey to conclude that an individual's income is
related to her occupational status
B. Concluding that a particular brand of fish food leads to faster fish growth, based on
your friend's observations
C. Using the results of an experiment in different local gardens to conclude that a new
plant fertilizer leads to sweeter-tasting tomatoes
D. Concluding that the fertility rate in third-world counties is related to the labor force
participation rate for women, based on official census statistics
E. None of the above
8. You're interested in drawing some conclusions about the political attitudes of college
under graduates. Your objective is to administer a survey to a representative sample of
students. Which of the following is true?
A. It's necessary to set up an experiment with control and treatment conditions to
properly~ collect representative data.
B. It's likely that using this approach will only identify a sample of males.
C. Your approach will produce anecdotal rather than available data.
D. There's no way to ensure that your sample will be representative of all college seniors.
E. By choosing only seniors, your sample won't be a representative sample of students.
9. A plant researcher identifies a sample of plots of land to examine the effect of a new
fertilize on the speed of growth of a particular crop. She treats half the plots of crops with
the new fertilizer (NewFert), and the other half with the more traditional brand
(FertiWhammo) She observes that crop growth in both sets of plots is almost identical.
The data collection strategy she has used is a (an):
A.
B.
C.
D.
E.
experiment.
anecdotal study.
observational study.
survey analysis.
quasi-study.
10. You're interested in whether tutoring is more effective when the student volunteers to
be tutored. You compare the test scores of two groups of students: those who chose to go
to after-school tutoring sessions and those who are required to go to the sessions by the
school administration. This is an example of a (an):
A. experiment.
B. anecdotal study.
C. observational study.
D. survey analysis.
E. fieldwork study.
11. A researcher is conducting an experiment on the possible effects of a new pill on
weight loss among obese men and women. He has given the new pill to a sample of
women and an old pill to the men. The researcher is comparing the effects of the old vs.
new pills to see which group demonstrates the greatest percentage decrease in weight.
You believe that his design is flawed. The flaw in his design is:
A. There's no response variable in the experiment.
B. The experimenter did not give both pills to those in the treatment condition (the
females should get both the old and new pill).
c. You can't measure the effect of the new pill on the men, since none of them received
this treatment.
D. There are too many treatment conditions in the experiment.
E. None of the above
12. An observational study based on survey data concluded that individuals who took
more vitamin C were able to recover from the flu faster. You want to replicate this study
using an experimental approach. The treatment in this experiment might be:
A. how long it takes to recover from the flu, in days.
B. whether an individual took vitamin C in a pill form or liquid form.
c. the amount of vitamin C taken per day: 0 mg, 1,000 mg, 2,000 mg, or 3,000 mg.
D. the change in body temperature over the period of the experiment.
E. All are acceptable treatments
13. Consider the following four studies:
I. A survey of newspaper editors examines their political views about foreign policy
issues.
The analysis and conclusion involves a summary of the survey results.
II. Third graders are randomly sampled and assigned to an intensive language course.
Their
performance on a year-end language test is compared to students who did not take the
course.
III. A study compares the change in home values between 1990-1999 in ten different
neighborhoods in Seattle. The results show that there's a higher percentage change over
time in less affluent neighborhoods.
IV. A study compares the durability of machine parts. The comparison looks at machines
that were purchased with new metal alloy parts and at those purchased with old metal
alloy parts.The results show that durability increases with the use of the new alloy.
Which examples are experiments?
A. I and II
B. II and IV
C. Only I
D. Only II
E. III and IV
14. Many statisticians say that the U.S. Census, which attempts to count every population
member directly, is significantly less accurate than a count estimated by random
sampling. Why might a count estimated from random samples be more accurate than a
census? (Choose the best answer.)
A. Random samples are scientific whereas censuses are not.
B. A true census takes so long that by the time all population members are counted, the
population has changed.
c. A census often can't find every population member, so some groups (such as the
homeless) are often under-represented.
D. A census is a haphazard sample, and census takers may be bribed by households.
E. A census is an old method written into law before anyone knew anything about
statistics.
15. Which of the following is the best representative sample of the adult population in the
United States?
A. Simple random sample of 10,000 adults from different city phone books
B. Simple random sample of 10,000 voters from across the country
c. Sample of 50,000 individuals at the Super Bowl (which draws from all over the
country)
D. Simple random sample of 1,000 adults from across the country
E. Sample of 50,000 members of AARP (American Association of Retired Persons)
Questions on the Vocabulary of Experiments and Surveys
16. A block is best described as:
A. the use of chance to divide experimental units into groups.
B. a design in which neither the experimenter nor the subject knows who is in the
treatment group and who is in the control group.
c. a group of subjects that are similar in some way known to affect the response to the
treatment.
D. the policy of repeating an experiment on different subjects to reduce chance variation
and to determine the generalizability of the findings.
E. the tendency of subjects to respond favorably to any treatment.
17. Replication is best described as:
A. the use of chance to divide experimental units into groups.
B. a design in which neither the experimenter nor the subject knows who is in the
treatment group and who is in the control group.
c. a group of subjects that are similar in some way known to affect the response to the
treatment.
D. the policy of repeating the experiment on different subjects to reduce chance variation
and to determine the generalizability of the findings.
E. the tendency of subjects to respond favorably to any treatment.
18. Double-blind is best described as:
A. the use of chance to divide experimental units into groups.
B. a design in which neither the experimenter nor the subject knows who is in the
treatment group and who is in the control group.
c. a group of subjects that are similar in some way known to affect the response to the
treatment.
D. the policy of repeating the experiment on different subjects to reduce chance variation
and to determine the generalizability of the findings.
E. the tendency of subjects to respond favorably to any treatment.
19. The placebo effect is best described as:
A.the use of chance to divide experimental units into groups.
B. a design in which neither the experimenter nor the subject knows who is in the
treatment group and who is in the control group.
c. a group of subjects that are similar in some way known to affect the response to the
treatment.
D. the policy of repeating the experiment on different subjects to reduce chance variation
and to determine the generalizability of the findings.
E. the tendency of subjects to respond favorably to any treatment.
20. Which of the following are considered to be important principles of experimental
design?
I. Control
II. Randomization
III. Replication
A. I only
B. II only
C. I and II only
D. I and III only
E. I, II, and III
21. A primary purpose of randomization is:
A. to minimize the placebo effect.
B. to avoid having to use a complicated double-blind procedure.
c. to eliminate bias between treatment groups.
D. to reduce variability within treatment groups.
E. to assist in developing a matched-pairs procedure.
22. A primary purpose of blocking is:
A. to minimize the placebo effect.
B. to avoid having to use a complicated double-blind procedure.
c. to eliminate bias between treatment groups.
D. to isolate the separate effects of the treatment and another important variable.
E. to assist in developing a matched-pairs procedure.
23. An experiment is conducted in which a series of tests are performed on pairs of
identical twins who were raised separately. A comparison of scores on each pair of twins
is used for analysis. This is best described as:
A. a matched-pairs procedure.
B. a double-blind procedure.
c. a randomized treatment group procedure.
D. a procedure with two explanatory variables.
E. an example of the placebo effect.
24. True of False: A doctor gives a pill to a patient, and the patient gets better. This must
be an example of the placebo effect.
Questions on Designs for Experiments
25. You're going to test two new varieties of fish food vs. a commonly used fish food.
You set up an experiment as follows: 60 fish are randomly assigned to each of three
different tanks. One tank is randomly selected to receive one of the new foods, another
tank to receive the other new food, and the third tank to receive the common food. Fish
growth is measured over time. This is an example of:
A. a randomized block design.
B. a double-blind matched pairs' design.
c. a completely randomized design with no control group.
D. a comparative block design.
E. a completely randomized design with a control group.
26. Say you're designing an experiment that looks at the effect of different types of newly
developed fish food on the growth rate of the fish. The treatments are new food A and
new food B; the control is the old food. You believe that the effects of the different types
of food on fish growth will vary for goldfish vs. tiger fish vs. guppies. How could you
design an experiment so that you're blocking on the species offish?
A. Eliminate one of the treatment conditions.
B. Match three different fish (one goldfish, one guppy, and of one tiger fish) on a set of
characteristics such as weight and length and then randomly assign them to different
tanks.
c. Only measure fish growth in the two treatment conditions.
D. First separate the fish into the three species. Then within each species, randomly
assign each fish to a treatment.
E. All of the above.
27. You're designing an experiment that looks at the effect of different types of newly
developed fish food on the growth rate of three species of fish: tiger fish, guppies, and
goldfish. The treatments are new food #1, new food #2, and old food. For a randomized
block design, blocked on species of fish, how many treatment groups would you have?
(Think of "old food" and one of the treatments.)
A. 3
B. 5
c. 6
D. 9
E. 12
28. 50 boys and 50 girls with ADD (Attention Deficit Disorder) were selected for an
experiment to test a new drug for the treatment of ADD. Half of the boys and half of the
girls were selected at random to receive the new drug, and the other half of each group
received a placebo. A reduction in symptoms of ADD was measured for each subject.
The basic design of this experiment is:
A. completely randomized.
B. completely randomized with one factor, gender.
C. randomized block, blocked by drug and gender.
D. randomized block, blocked by drug.
E. randomized block, blocked by gender.
29. Let's say you're interested in the effects on boys of different dosage levels of a new
drug for the treatment of Attention Deficit Disorder (ADD). You set up an experiment to
consider the factor of dosage with two levels (300 mg vs. 500 mg). What would be the
different treatment groups of the experiment within each block?
A. Three groups: no drug/300 mg of new drug/500 mg of new drug.
B. Three groups: placebo drug/300 mg of new drug/500 mg of new drug
C. Two groups: 300 mg of new drug/500 mg of new drug.
D. Four groups: 300 mg of new drug/300 mg of placebo drug/ 500 mg of new drug/500
mg of placebo drug
E. Two groups: placebo drug/either 300 or 500 mg of new drug.
30. You've read a story in The New York Times claiming that individuals who engage in
aerobic exercise for at least an hour a day demonstrate fewer symptoms of depression.
You read that an experiment was conducted in which a researcher first administered a
survey on depression and self-esteem to 100 individuals and then taught them some
proper techniques of aerobic exercise. The 100 individuals were then sent off to exercise
at least one hour a day. After two months, the depression and self-esteem survey was
administered again and showed that depression symptoms declined and self-esteem
increased. The experimental design used here is a:
A. matched pairs design in which subjects are matched on a set of characteristics before
random assignment.
B. matched pairs before and after design.
C. completely randomized design.
D. randomized block design, blocked on form of exercise and gender.
E. quasi design.
Questions on Types of Samples for Surveys
31. A company wants to obtain information on students aged 17 to 22. This company
randomly selects 2,000 students from the mailing lists of four universities. (Every student
attending one of these universities is on the respective mailing lists.) Then the company
sends the questionnaires to the sample of 2,000. What type of sample is this?
A. A representative sample of students aged 17 to 22 at these four universities.
B. A stratified random sample of students aged 17 to 22 at these four universities.
c. A simple random sample of all students at these four universities.
D. A stratified random sample of all students at these four universities.
E. A multi-stage random sample of all students at these four universities.
32. For a semester project, a student needs to select a random sample of 10 students from
his senior class of 250. He carefully numbers the class list from 000 to 249 and then uses
a random number generator to obtain 3-digit random numbers. The 10 unique numbers
are his sample. He notices that they all belong to the same honors AP Calculus class.
Another student claims that this could not be a random sample. Which of the following is
true?
A. The sample drawn is so unlikely that it could not be considered a random sample.
B. Since the selected students are not representative the entire senior class, this is not a
random sample.
c. Whether a sample is a random sample or not is determined by the sampling method,
not the results. The method used here is OK. .
D. A sample size of 10 is too small to be a random sample of 250.
E. The class should have been numbered from 001 to 250 rather than from 000 to 249 to
produce a better random sample.
33. An important reason a market researcher collects data using a stratified random
sample rather than a simple random sample is:
A. to collect data at a lower cost.
B. to eliminate, or a least reduce, bias.
c. to make a representative sample more likely than one produced by simple random
sampling.
D. convenient data collection.
E. to have a systematic way of obtaining the data.
34. Which of the following would generate an SRS of 50 integers from 5 to 25 on the TI 83?
A. randNorm(5,25,50)
B. randlnt(50,5,25)
C. rand(5,25,50)
D. 50. randlnt(5,25)
E. randInt(5,25,50)
35. True or False: Blocking in an experiment and stratifying in a survey accomplish the
same thing. They control the amount of variation in key characteristics within the total
sample, such as race or gender, that are likely to be important to the outcome of interest.
36. Consider the following four rows from a random number table:
55588
46563
12975
72321
99404 70708 41098
56934 48394 51719
13258 13048 45144
81940 00360 02428
Use the random number table above to draw a sample size of 10. Twenty percent of the
population has a trait you wish to find. A success is defined as a 0 or 1. Draw eight
samples of size 10 by reading each row from left to right. What are the greatest and
fewest number of successes you might expect in a sample of size 10?
A. 4,1
B. 3,0
C. 4,0
D. 3, 1
E. 4,2
Questions on Bias in Surveys
37. Which of the following are true statements?
I. Under-coverage bias can be overcome by greatly increasing the sample size.
II. Well-designed probability sample always eliminate bias.
III. Response bias results only from the wording of survey questions.
A. I only
B. n only
C. III only
D. n and III
E. None ofthese
E. None of these. There may be some truth in each statement, but none of them are alway
true.
38. A random sample of 15,000 people is selected from local telephone books; 3,000
return the questionnaire. This survey suffers from:
I. Sampling bias
II. Response bias III. Question-wording bias
A. I only
B.II only
C. III only
D. I and II only
E. II and III only
39. A surveyor for a vegetarian magazine asks the following question as part of a survey:
"The U.S. Government subsidizes the cost of food and water for cattle. Given that most
agricultural land is for feeding and grazing cattle, while people starve to death, do you
favor taking away government subsidies, so the consumer pays the full price for beef?"
The survey appeared in a national magazine and readers were requested to return their
response to a provided address. This survey will most likely suffer from:
I. Sampling bias
II. Response bias
III. Question-wording bias
A. I only
B. II only
C. III only
D. II and III only
E. I, II and III
40. A poll found that 81 % of U.S. parents say they have spoken with their teenagers
about the
dangers of drinking and driving. Only 64% of teens of the same families say they
remember such a discussion. What type of bias is most likely at work here?
I. Sampling bias
II. Response bias III. Question-wording bias
A. I only
B. II only
C. III only
D. II and III only
E. I, II, and III
41) True or False: A finding is statistically significant if it's unlikely that it could have
occurred by chance.
42) True or False: By looking at the numbers you can tell if the sampling or the way the
measurements were taken was biased.
43) Virginia is going to use a systematic sample to choose a sample of 1/10 of her
sophomore class. She looks in the first ten 'names and sees the name of her friend Elena
there. She figures that Elena would like to be in the survey, so she begins her systematic
sample there. Then she selects every tenth name on the alphabetical list after that. Which
of the following statements are true?
I. Her sample is not a probability sample.
II. By including Elena, she has increased the likelihood of a response bias. III. Her
sample suffers from under-coverage.
A. I only
B. II only
C. I and II
D. I and III
E. I, II, and III
Questions on Factors Causing Bias
44) You're shopping for a car, and you log on to a Web site that gives reviews for
automobiles. Reviews are written by average people who bought the cars and want to
share their experi- ences with others. You look up the reviews for a Toyhushusta Bearcat
sport truck, and find that 79% of the reviewers checked the "I would not buy this truck
again" box. Based on that and nothing else, you decide not to buy the truck. Why was
your decision too hasty?
A. The poll question is leading and poorly worded.
B. The sample size is too small to make any statistical conclusions.
C. It's reasonable to assume that a large percentage of the respondents are lying.
D. Undercoverage and voluntary response bias.
E. There is no control condition in this study.
45. All of the following are examples of a sample that suffers from an undercoverage bias
except:
A. An estimate of an election outcome based on a sample of voters' names taken from
automobile registrations.
B. A poll on Missouri dentist's attitudes, based on questionnaires sent to a registry of
attendees at the largest dental convention in the state.
C. The mean income of U.S. citizens, based on Census data.
D. A random sample of 5,000 U.S. adults with survey data collected via e-mail.
E. A simple random sample of licensed drivers, taken from driver-licensing records.
46. Consider a survey in which 79% of the respondents said yes to the following
question:
Agree or disagree: Since our economy can't sustain itself without a healthy environment,
it's important that Congress pass laws to protect the environment.
What's a reasonable reaction to the survey results?
A. They're not valid, due to undercoverage.
B. They're not valid, due to voluntary response bias.
C. They're not valid, due to a leading question.
D. I totally agree. We need laws that protect the environment.
E. I disagree. We don't need laws that protect the environment.
47. A telephone research agency has been contracted to collect survey information on
buying habits of teenagers, aged 16 and 17. The agency conducts phone calls between 3
P.M. and 4:30 P.M. each weekday. The survey finds that the majority or teenagers aged
16 and 17 have access to a credit card. Which of the following is the most likely problem
with this analysis?
A. This is a voluntary response sample, and only affluent youths will answer the survey.
B. The respondents were not randomly selected.
C. The survey questions are leading and influence the way affluent youths respond.
D. The sample suffers from undercoverage due to the hours when polling took place.
E. The respondents were being untruthful.
48. A university involved in conducting social science experiments and surveys places an
ad- vertisement in the c1assifieds to hire a racially and ethnically diverse set of
individuals to administer surveys. The surveys will assess opinions on welfare policy and
discrimination. The university plans to use a random sample of these new employees to
help conduct an upcoming experiment with a random sample of individuals in a major
city. By hiring this di- verse group of employees, the university is hoping the reduce the
problems of
in the experiment.
A. undercoverage
B. interviewer-induced bias
C. a Hawthorne effect
D. reverse blocking
E. voluntary response bias
49) You're a wildlife biologist who wants to measure the top speed of a particular species
of dragonfly. You set up a measurement apparatus in a portable wind tunnel, where the
insect is suspended in place while air blows over it. The wind tunnel blows air at an
increasing speed, and you track the point at which the beating of the insect's wings can't
keep pace with the rate of air flowing over them. You plan to travel all over South
America, setting up your portable wind tunnel in exotic locations, capturing insects, and
measuring their maximum speeds.
What is a potential source of bias in this study?
A. Voluntary response bias
B. A biased sample
C. Experimenter-induced bias
D. U ndercoverage
E. Response bias
50) A firm administers a survey in the state ofN ew York. The survey is mailed out to a
random set of 5,000 households throughout the state, and responses are received from
200 households. The two key questions on the survey are:
I) Whom do you plan to vote for in the upcoming Senate election, the Democratic or
Republican candidate?
2) Do you agree with the idea of imposing limits on the amount of time a Senator can
spend in office?
What is a possible problem with this survey?
A. Voluntary response bias
B. Undercoverage bias
C. Leading questions
D. Stratified original sample
E. All of the above
Chapter 5 Practice Answers
1) E. It gathers data from every member of a population. A census contacts every
population member for info, although this is often difficult and usually not achieved.
There’s a tendency to undercount individuals who are difficult to locate. Sampling is
often a more accurate technique because of the limitations of gathering data from an
entire population.
2) False.
3) A. I only.
4) D. I and II only.
5) C. This is an example of anecdotal evidence and shouldn’t be used to make a decision
about wearing seat belts.
6) A. This is an experiment, since you imposed a treatment on some subjects and left
others untreated.
7) B. Concluding that a particular brand of fish food leads of faster fish growth based on
the observations of your friend.
8) E. By choosing only seniors, your sample won’t be a representative sample of
students.
9) A. Experiment, since the researcher exerts some control over some of the variables.
10) C. Observational Study; your simply measuring the performance of two different
groups; you have no influence on the independent or dependent variable. If this were an
experiment, you would have assigned the students to the two different groups.
11) C. You can’t measure the effect of the new pill on the men, since none of them
received the this treatment.
12) C. The amount of vitamin C taken per day: 0 mg, 1,000 mg, 2,000 mg, or 3,000 mg.
13) D. Only II.
14) C. Some groups (such as the homeless) are under-represented.
15) D. Sample of 1,000 adults randomly chosen across the country.
16) C. A group of subjects that are similar in some way known to affect t the response to
the treatment.
17) D. The policy of repeating the experiment on different subjects to reduce chance
variation and to determine the generalizability of the findings. Replication is repetition of
the experiment.
18) B.
19) E. The tendency of subject to respond favorably to any treatment.
20) E. I, II, and III. All three are important principles of experimental design.
21) C. To eliminate bias between treatment groups.
22) D. To isolate the separate effects of the treatment and another important variable. If
we block, or divide the sample based on some important variable we know to have an
effect on the response (such as gender), we can separate the effects of the treatment from
the effect of the blocking variable.
23) A. The twins make a natural matched pair for some kinds of experiments in which
one might want to match subjects as closely as possible on biological characteristics.
24) False. The question doesn’t give any information about the design of the study, so we
don’t know whether or not this observation is a true effect of a treatment or an example
of the placebo effect.
25) E. This is the simplest type of experiment.
26) D.
27) D.
28) E.
29) B.
30) B.
31) C.
32) C.
33) C.
34) E. RandInt (5, 25, 50). The randInt function produces a random number between the
first and second numbers you specify. The third number is the number of times you want
a random number generated.
35) True. The main difference between them is that no treatments are applied to samples
that are stratified, whereas experimental treatments are applied within blocks.
36) C. 4, 0; The winning blocks of ten are in bold:
55588 99404 70708 41098 (4 instances)
46563 56934 48394 51719 (0 instances)
12975 13258 13048 45144
72321 81940 00360 02428 (4 instances)
37) E. None of these. There may be truth in each statement, but none of them are always
true.
38) D. I and II only. There's certainly under-coverage, which is a sampling bias, and
there's non- response bias, which is one kind of response bias. There's no indication that
the wording is an issue.
39) E. I, II and III. Since this was in a vegetarian magazine, meat eaters were underrepresented in the sample, which creates sampling bias. Readers who feel most strongly
about the issue will more likely to return the survey, resulting in response bias. The
question is designed to elicit agreement with the statement, so there's question-wording
bias, too.
40)E: II only. Parents are probably falling prey to the untruthful, or socially acceptable,
answer. They don't want anyone to think they're bad parents.
41) True. When there's a very low chance that a result could have occurred by chance,
then it is statistically significant. This indicates that something other than chance may be
influencing the result.
42) False. You may be able to get a few clues about potential bias this way, but you really
have to examine the entire study design process to understand bias, not just look at the
study results.
43) C. I and II. A systematic sample is a probability sample, but only when the first name
i! selected randomly. Some response bias has probably been increased by choosing Elem
(although the bias may be very small). Because Elena is a friend of Virginia's, she's mon
likely to answer the survey and to share Virginia's views.
44) D. undercoverage and voluntary response bias. This kind of survey may be fine for
giving you ideas to think about, but it's not reliable enough to base a decision solely on it.
Visitors to the Web site don't represent the entire population. Also, people who feel most
strongly about the issue are more likely to respond. In some cases people who volunteer
to respond are the ones who feel negatively about the issue, and that might explain why
so many of the respondents wouldn't buy the truck again.
45) E. a simple random sample of licensed drivers, taken from driver-licensing records.
In this example, the sampling frame covers the entire population: licensed drivers.
46) C. they're not valid, due to a leading question. This question makes the agree position
seem more reasonable.
47) D. the sample suffers from undercoverage. Many teenagers aren't at home during
those hours, and many of those who are at home are likely to share traits that could bias
the survey results.
48) B. interviewer-induced bias. The concern in such an experiment is that the
interviewers' race will affect the respondents' answers. Since responses to the topic of
discrimination could potentially be affected by interviewer-induced bias, a way to reduce
some of the problems is to use a diverse mix of interviewers and to examine whether the
race of the interviewer is adversely affecting the response variable.
49) B. a biased sample. The insects you capture are likely to be easier to catch (and
possibly slower) than the population as a whole.
50) Voluntary response bias. This is a type of response bias in which the people who
choose to respond may hold opinions that are different from the majority of the
population.