Seeing Through Statistics 4th Edition by Jessica M. Utts – Test Bank

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CHAPTER 5

EXPERIMENTS AND OBSERVATIONAL STUDIES

SECTION 5.1

DEFINING A COMMON LANGUAGE

FREE RESPONSE QUESTIONS

For Questions 1-3 use the following narrative

Narrative: Toy colors

Suppose a toy company wants to know if certain colors are more appealing and attractive to toddlers

than others. They decide to measure this by choosing five colors of blocks and making sets of blocks in

each of the five colors. Then they found 30 toddlers to participate in the study, and they randomly

assigned each toddler a block color. They observed each toddler separately at the same time of the day,

and gave them no other toys to play with. They recorded the length of time each toddler played with

the blocks, to see if some colors of blocks were played with longer than other colors. All toddlers in

the experiment were the same age (2 years old) and an equal number of girls and boys played with

each color of blocks.

1. {Toy colors narrative} What is the explanatory variable and what is the response variable?

ANSWERS (RESPECTIVELY): BLOCK COLOR AND PLAYING TIME.

2. {Toy colors narrative} Is this study an observational study or an experiment?

ANSWER: EXPERIMENT

3. {Toy colors narrative} Name one confounding variable that was controlled for in this study.

ANSWER: ANY OF THE FOLLOWING: AGE; TIME OF DAY; GENDER; OTHER

TOYS; INTERACTION WITH OTHER CHILDREN. BOREDOM WITH BLOCKS IS

ALSO CONTROLLED FOR BECAUSE EACH TODDLER PLAYED WITH ONE

COLOR.

4. Give two reasons why we must sometimes use an observational study instead of an experiment.

ANSWER: 1) IT IS UNETHICAL OR IMPOSSIBLE IN CERTAIN SITUATIONS TO

ASSIGN PEOPLE TO RECEIVE A SPECIFIC TREATMENT (SUCH AS SMOKING); 2)

CERTAIN EXPLANATORY VARIABLES, SUCH AS LEFT VS. RIGHT HANDEDNESS,

ARE INHERENT TRAITS AND CANNOT BE RANDOMLY ASSIGNED.

MULTIPLE CHOICE QUESTIONS

5. Which of the following describes an experiment?

a. b. Create differences in the explanatory variable and then examine the results.

Observe differences in the explanatory variable and then notice whether these are related

to differences in the response variable.6. 7. 8. c. d. Both a) and b) are experiments.

Neither a) nor b) are experiments

ANSWER: A

Which of the following is a property of a confounding variable?

a. It is related to the explanatory variable; individuals who differ on the explanatory

variable are also likely to differ on the confounding variable.

b. c. It affects the response variable.

Its effect on the response variable cannot be separated from the effect of the explanatory

variable on the response variable.

d. All of the above

ANSWER: D

What is the effect of recruiting volunteers to participate in a randomized experiment?

a. The results will be more credible because people who really wanted to participate took

part in the study.

b. c. The results cannot necessarily be extended to the larger population.

There will be no effect because the people are always randomly assigned to treatments,

eliminating any type of bias.

d. Researchers are never allowed to use volunteers to participate in an experiment.

ANSWER: B

What does randomization mean in terms of experiments?

a. Each of the experimental units is randomly selected to participate.

b. Each of the experimental units is randomly assigned to a treatment.

c. The researchers randomly select which treatments they will include in the experiment.

d. None of the above.

ANSWER: B

9. 10. FILL-IN-THE-BLANK QUESTIONS

A(n) __________ variable is one that attempts to explain or is purported to cause (at least

partially) differences in a(n) __________ variable.

ANSWERS (RESPECTIVELY): EXPLANATORY; OUTCOME (OR RESPONSE)

One of the major advantages of an experiment over an observational study is that in an

experiment, the researcher attempts to control for __________ variables.

ANSWER: CONFOUNDING

SECTION 5.2

DESIGNING A GOOD EXPERIMENT

FREE RESPONSE QUESTIONS

11. What is one advantage of using a matched-pairs design in a randomized experiment?ANSWER: EACH PERSON IN THE STUDY SERVES AS HIS/HER OWN CONTROL;

NATURAL VARIABILITY IN THE RESPONSE VARIABLE FROM PERSON TO

PERSON DOESN’T OBSCURE THE EFFECTS OF THE TREATMENT.

For Questions 12-13 use the following narrative

Narrative: BMD

A recent magazine article stated that bone mineral density (BMD) may one day predict breast

cancer risk in older women, according to a study in the Journal of the National Cancer Institute.

Researchers followed the health of 8,905 women who were 65 or older and initially cancer free.

Eventually 315 participants developed breast cancer. Women with the highest BMD were almost

three times more likely to develop breast cancer, compared to the women with low BMD. (Better

Homes and Gardens, October 2001, page 224.)

12. {BMD Narrative} Do the results of this study mean that a high bone mineral density (BMD)

causes breast cancer in older women? Explain your answer.

ANSWER: NO; IT IS JUST PREDICTIVE AT THIS POINT. THIS WAS AN

OBSERVATIONAL STUDY, AND THERE COULD BE MANY CONFOUNDING

VARIABLES.

13. {BMD Narrative} Explain why it is not possible to conduct a randomized experiment in this

situation.

ANSWER: IT IS NOT POSSIBLE TO RANDOMLY ASSIGN WOMEN TO EITHER A

LOW OR HIGH BMD; IT WOULD ALSO BE UNETHICAL TO FORCIBLY CREATE A

HIGH BMD FOR A GROUP OF WOMEN AND SEE IF THIS INCREASES THEIR

CHANCES OF DEVELOPING BREAST CANCER.

14. Using 20 pairs of identical twins to participate in a study containing a treatment and a control is an

example of what type of experimental design?

ANSWER: MATCHED-PAIRS

MULTIPLE CHOICE QUESTIONS

15. 16. 17. Which of the following defines what is meant by a control group in an experiment?

a. A group that is handled identically to the treatment group(s) in all respects except that

they are controlled to a greater extent than the other groups, providing baseline data.

b. c. A group that is used by researchers to monitor how the experiment is going.

A group that is handled identically to the treatment group(s) in all respects except that

they don’t receive the active treatment.

d. None of the above.

ANSWER: C

Which of the following is not true about placebos?

a. b. c. d. Placebos can be very effective in producing a response.

Placebos are only useful if the subject is blind as to whether or not they receive one.

Participants assigned a placebo are part of the control group of an experiment.

All of the above are true statements.

ANSWER: D

Which of the following is implemented in an experiment to reduce unknown systematic biases due

to confounding variables that might otherwise exist between treatment groups?

a. Randomization

b. Blocks

c. Repeated measures

d. All of the above18. ANSWER: A

Which of the following is implemented in an experiment to reduce known sources of natural

variability in the response variable, so that differences due to the explanatory variable can be

detected more easily?

a. Matched-pairs

b. Repeated measures

c. Blocks

d. All of the above

ANSWER: D

19. 20. FILL-IN-THE-BLANK QUESTIONS

Experiments use __________ to reduce the effects of confounding variables and other sources of

bias that are naturally present in observational studies.

ANSWER: RANDOMIZATION

A(n) __________ experiment is one in which neither the participant nor the researcher taking the

measurements knows who had which treatment.

ANSWER: DOUBLE-BLIND

SECTION 5.3

DIFFICULTIES AND DISASTERS IN EXPERIMENTS

FREE RESPONSE QUESTIONS

21. Discuss the biggest problem with using volunteers to participate in an experiment.

ANSWER: THE RESULTS ARE DIFFICULT TO GENERALIZE TO THE INTENDED

POPULATION.

22. 23. 24. A group of volunteers is clearly not a random sample from the population, yet volunteers are often

used in experiments. Explain why.

ANSWER: IT IS IMPRACTICAL AND MANY TIMES UNETHICAL TO SUBJECT

SOMEONE TO AN EXPERIMENT WITHOUT THEM VOLUNTEERING FOR IT.

Name two ways in which an experimenter can bias the results in a poorly designed experiment.

ANSWER: ANY REASONABLE ANSWERS OK. EXAMPLES: RECORDING THE DATA

ERRONEOUSLY TO MATCH THE DESIRED OUTCOME; TREATING SUBJECTS

DIFFERENTLY BASED ON WHICH CONDITION THEY ARE RECEIVING (NOT

BEING BLINDED); SUBTLY LETTING THE SUBJECTS KNOW THE DESIRED

OUTCOME; EXPERIMENTER EFFECT.

Give an example of an experiment in which it would be unethical to give the control group a

placebo.

ANSWER: ANY REASONABLE ANSWER OK. EXAMPLE: IN A STUDY OF A NEW

DRUG FOR AIDS, THE CONTROL GROUP SHOULD GET THE STANDARD AIDS

TREATMENT, NOT A PLACEBO.MULTIPLE CHOICE QUESTIONS

25. Which of the following influences on the experimental units can bias the results of an experiment?

a. Placebo effect

b. Hawthorne effect

c. Not being blinded

d. All of the above

ANSWER: D

26. Which of the following describes an experiment with little or no ecological validity?

a. b. c. An experiment that is harmful to the environment and can’t be justified.

An experiment whose results are not ecologically beneficial.

An experiment whose variables are measured in an artificial setting and whose results do

not accurately reflect the real world.

d. None of the above.

ANSWER: C

27. Which of the following is a potential complication of a poorly designed/conducted experiment?

a. Confounding variables

b. Interacting variables

c. Hawthorne effect

d. All of the above

ANSWER: D

28. Which of the following statements is true?

a. A placebo can have a strong effect on experimental outcomes because the power of

suggestion is somehow able to affect the result.

b. Participants in an experiment tend to respond differently than they otherwise would, just

because they are in an experiment.

c. The expectations of an experimenter can really influence the results.

d. All of the above.

ANSWER: D

29. 30. FILL-IN-THE-BLANK QUESTIONS

If the experimental units as a group do not represent the intended population, the researcher cannot

__________ the results from the experiment to the intended population.

ANSWER: GENERALIZE

In an experiment to see if a certain new drug can prevent a second heart attack, other drugs that

the experimental units may or may not be taking already for heart related illnesses would be

considered to be __________ variables.

ANSWER: INTERACTING

SECTION 5.4

DESIGNING A GOOD OBSERVATIONAL STUDYFREE RESPONSE QUESTIONS

31. Discuss the main difference between a case-control study and a matched-pairs experiment (other

than the fact that one is an observational study and one is an experiment).

ANSWER: IN A CASE-CONTROL STUDY THE RESEARCHER DOES NOT

RANDOMLY ASSIGN TREATMENTS WITHIN PAIRS BUT IS RESTRICTED TO HOW

THEY OCCUR NATURALLY (FOR EXAMPLE RIGHT VS LEFT HANDED). ALSO,

NOT ALL CASE-CONTROL STUDIES MATCH CASES AND CONTROLS.

32. The case-control design has some clear advantages over randomized experiments as well as over

other observational studies. Name two of those advantages.

ANSWER: ANY TWO OF THE FOLLOWING ARE OK: EFFICIENCY IN TERMS OF

TIME OR MONEY; NOT HAVING TO WORRY ABOUT THE ETHICS INVOLVED IN

RANDOMLY ASSIGNING PEOPLE TO EITHER HARMFUL OR BENEFICIAL

TREATMENTS; AND INCLUSION OF ENOUGH PEOPLE WITH THE CONDITION

YOU ARE STUDYING.

33. Which type of observational study gives you better quality data, a retrospective study or a

prospective study, and why?

ANSWER: A PROSPECTIVE STUDY IS A BETTER PROCEDURE BECAUSE PEOPLE

OFTEN DO NOT REMEMBER PAST EVENTS ACCURATELY.

34. Name one disadvantage and one advantage of an observational study over an experiment.

ANSWER: DISADVANTAGE – THE RESEARCHERS OBSERVE, BUT CANNOT

CONTROL, THE EXPLANATORY VARIABLES. ADVANTAGE – THEY ARE MORE

LIKELY TO MEASURE PARTICIPANTS IN THEIR NATURAL SETTING (AND DO

NOT MANIPULATE THEIR ENVIRONMENT).

MULTIPLE CHOICE QUESTIONS

35. 36. In order to establish a connection between an explanatory and response variable in an

observational study, what is needed?

a. b. Statistical methods that examine the connection.

A comparison to determine if changes in the explanatory variable are related to changes

in the response variable.

c. Either a) or b)

d. You can never establish a connection between an explanatory and a response variable

without doing a randomized experiment.

ANSWER: C

Which of the following is not a type of observational study?

a. Case-control study

b. Retrospective study

c. Prospective study

d. Introspective study

ANSWER: D

37. It is the purpose of what type of study to find out whether one or more explanatory variables are

related to a certain disease (for example whether smoking causes lung cancer)?

a. Case-control study

b. Matched-pairs experiment

c. Block design

d. None of the aboveANSWER: A

38. Which of the following statements about case-control studies is false?

a. b. Case-control studies have some clear advantages over randomized experiments.

A properly designed case-control study does a good job of reducing potential

confounding variables.

c. Any controls that are selected will improve the quality of the results of the study.

d. None of the above.

ANSWER: C

FILL-IN-THE-BLANK QUESTIONS

39. An observational study that asks participants to recall their first childhood memory is a(n)

__________ study.

ANSWER: RETROSPECTIVE

40. An observational study that follows a group of high school students into the future, recording how

many children they have (if any) and at what age(s) they had those children is an example of a(n)

__________ study.

ANSWER: PROSPECTIVE

SECTION 5.5

DIFFICULTIES AND DISASTERS IN OBSERVATIONAL STUDIES

FREE RESPONSE QUESTIONS

41. 42. A common mistake made by the media, the general public, and some researchers, is to think that a

link between two variables in any study implies that one variable causes the other. Explain what is

wrong with this automatic conclusion.

ANSWER: IF THE LINK IS BASED ON AN OBSERVATIONAL STUDY, THERE IS

SIMPLY NO WAY TO RULE OUT ALL POTENTIAL CONFOUNDING FACTORS, SO

CAUSE AND EFFECT CANNOT BE ESTABLISHED.

How can a researcher try to address the problem of confounding variables when designing an

observational study?

ANSWER: MEASURE ALL THE POTENTIAL CONFOUNDING VARIABLES HE/SHE

CAN THINK OF AND INCLUDE THEM IN THE ANALYSIS TO SEE WHETHER THEY

ARE RELATED TO THE RESPONSE VARIABLE; OR USE A CASE-CONTROL STUDY

AND CHOOSE THE CONTROLS TO BE AS SIMILAR AS POSSIBLE TO THE CASES .

For Questions 43-44 use the following narrative

Narrative: Girls’ grades

A 1998 study by the Horatio Alger Association was summarized in USA Today by saying that

high-school girls outperform boys in school. The article was titled “Study: Girls get higher grades”

(USA Today 8/12/ 98). The study was based on a survey of 1,195 randomly chosen students aged

14-18. Among the findings: One third of the girls said they ‘received mostly A’s on their last

report card’ compared to only one-fifth of the boys. Three-fourths of girls ‘believe they will have

many opportunities available to them after they graduate’ compared to only two-thirds of the boys.43. 44. {Girls’ grades narrative} Do you think the conclusions of this study are justified? Why or why

not?

ANSWER: NO, FOR A VARIETY OF REASONS. STUDENTS SELF-REPORTED THEIR

GRADES; MAYBE GIRLS AT THAT AGE OVERESTIMATE THEMSELVES, OR BOYS

UNDERESTIMATE THEMSELVES (OR REPORTED THEIR GRADES MORE

ACCURATELY); MANY CONFOUNDING VARIABLES EXIST, SUCH AS SELF-

ESTEEM; SOCIO ECONOMIC STATUS; GENDER; HOW THE STUDENTS WERE

ASSESSED, ETC.

{Girls’ grades narrative} How would you change this study in order to improve the quality of the

results?

ANSWER: ANY REASONABLE ANSWER OK. EXAMPLES: OBTAIN THE GRADES

FROM ACTUAL SCHOOL TRANSCRIPTS, NOT VIA SELF-REPORTING; MEASURE

OTHER CONFOUNDING VARIABLES SUCH AS SELF-ESTEEM.

MULTIPLE CHOICE QUESTIONS

45. Which of the following is a potential complication of observational studies?

a. Confounding variables

b. The improper conclusion of causation

c. Improper extension of the results

d. All of the above

ANSWER: D

46. What type of study often results in problems related to using the past as a source of data?

a. Case-control study

b. Retrospective study

c. Prospective study

d. Before vs. after matched-pairs experiment

ANSWER: B

47. 48. Which of the following studies can result in researchers extending the results inappropriately

because the sample doesn’t represent the intended population?

a. Studies involving volunteers (self-selected samples)

b. Studies involving convenience samples

c. Case-control studies

d. All of the above

ANSWER: D

An observational study based on a sample of students in introductory psychology classes at a

university in the Midwestern U.S. compared drinking behavior and hangover symptoms in men

and women. To what group can the results of this study definitely be extended?

a. All men and women

b. All men and women of the same age group as those in the study

c. All college students in the Midwestern U.S.

d. None of the above

ANSWER: D

49. FILL-IN-THE-BLANK QUESTIONS

One of the complications that can arise with observational studies is __________ variables and the

implications of causation.ANSWER: CONFOUNDING

50. One of the complications that can arise with observational studies is using the past as a source of

data. This type of study is called a __________ study.

ANSWER: RETROSPECTIVE

SECTION 5.6

RANDOM SAMPLE VERSUS RANDOM ASSIGNMENT

51. FREE RESPONSE QUESTIONS

What is the main purpose of using a random sample in a study?

ANSWER: SO THAT THE RESULTS CAN BE EXTENDED TO THE POPULATION

FROM WHICH THE SAMPLE WAS DRAWN.

52. What is the main purpose of using random assignment in experiments?

ANSWER: TO EVEN OUT CONFOUNDING VARIABLES ACROSS TREATMENTS

AND OPEN UP THE POSSIBILITY FOR A CAUSE AND EFFECT CONCLUSION.

53. Suppose you come across an experiment or observational study in which a random sample was not

used. To what extent can (should) the results be extended to a larger population?

ANSWER: IT DEPENDS ON THE EXTENT TO WHICH THE PARTICIPANTS IN THE

STUDY ARE REPRESENTATIVE OF THAT LARGER POPULATION IN TERMS OF

THE VARIABLES BEING STUDIED. THIS CAN BE SERIOUS ENOUGH TO NEGATE

THE CONCLUSIONS ALTOGETHER.

54. Suppose you come across an experiment in which random assignment was not used. To what

extent will the conclusions of the experiment be affected?

ANSWER: IT DEPENDS ON THE EXTENT TO WHICH YOU THINK THE

DIFFERENCES IN THE GROUPS (DUE TO NOT USING RANDOM ASSIGNMENT)

MAY EXPLAIN ANY OF THE OBSERVED RELATIONSHIPS. THIS CAN BE SERIOUS

ENOUGH TO NEGATE THE CONCLUSIONS ALTOGETHER.

MULTIPLE CHOICE QUESTIONS

55. Random sampling deals with what aspect of a study?

a. b. c. d. Who the results can be applied to.

Whether or not a cause and effect relationship exists.

What the actual statistical results are.

What research question is being asked.

ANSWER: A

56. Random assignment deals with what aspect of an experiment?

a. Who the results can be applied to.

b. Whether or not a cause and effect relationship exists.

c. What the actual statistical results are.

d. None of the above.

ANSWER: B57. 58. 59. 60. Without random sampling, which of the following can happen?

a. Naturally occurring confounding variables can result in an apparent relationship between

the explanatory and response variables.

b. c. The results may not be able to be extended to a larger population.

The researchers will have a much easier time getting participants for their study, resulting

in a larger sample size, and more accurate data.

d. None of the above

ANSWER: B

Without random assignment, which of the following can happen?

a. Naturally occurring confounding variables can result in an apparent relationship between

the explanatory and response variables.

b. c. The results may not be able to be extended to a larger population.

Many people in the study will drop out because they aren’t happy with the treatment they

were assigned to. This will cause bias in the results.

d. None of the above.

ANSWER: A

FILL-IN-THE-BLANK QUESTIONS

Random __________ is used to get a representative sample from the population of interest so the

results can be extended to that population.

ANSWER: SAMPLING

Random __________ is used to control for confounding variables and other possible sources of

bias, allowing for the possibility of a cause and effect conclusion.

ANSWER: ASSIGNMENT