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Observational Studies and Experiments — Quiz Answers

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1
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Which statement is a correct interpretation of these methods?

A
Method A is an experiment because it compares many brands of sunscreen, while method B is an observational study.
B
Both methods are observational studies because neither method attempts to influence responses.
C
Method B is an experiment because it randomly assigns volunteers a sunscreen, while method A is an observational study.
D
Both methods are experiments because sun exposure is assessed in both methods.
2
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Which method describes an observational study?

A
Method 1 is an observational study because many people can be surveyed.
B
Method 1 is an observational study because no attempt is made to influence results.
C
Both methods are observational studies because information on both types of detergent can be collected.
D
Method 2 is an observational study because volunteers assess the fabrics.
3

Which statement best describes the effect of the confounding variable?

A
Because golfers may use both magnetic bracelets and expensive golf clubs, it will be difficult to determine which variable contributes most to longer shots.
B
Because golfers purchase expensive golf clubs, they may stop wearing their magnetic bracelets, which would interfere with the outcome of the study.
C
Because golfers using the magnetic bracelets believe they are hitting longer shots, the study may show their shots are not as long as they believe.
D
Because golfers can be randomly assigned to receive either magnetic bracelets or expensive golf clubs, the expensive golf clubs are a confounding variable.
4

Which statement best describes the effect of the confounding variable?

A
Because owners of different types of vehicles may choose not to use the additive, those vehicles will not show an improvement in gas mileage.
B
Because vehicles of different colors may show differences in gas mileage, the additive may improve the gas mileage in some vehicles but not in others.
C
Because vehicles of different sizes may respond differently to the additive, it may be difficult to conclude whether the additive improves gas mileage for all vehicles.
D
Because vehicles of different sizes may respond similarly to the additive, it should be easy to conclude whether the additive improves gas mileage.
5

Which statement best describes the effect of the confounding variables?

A
If the half of the lawn with the new lawn food shows fewer weeds after a month, this will prove the new lawn food is better at stopping weed growth.
B
Because of confounding variables, the homeowner should only put the new lawn food on shady spots and the original brand on sunny spots.
C
The parts of the lawn that receive the new lawn food may also get more shade than other parts of the lawn, and the shade might also cause fewer weeds.
D
Because shade is a primary cause of weed growth, the brand of lawn food used in shady or sunny spots will not affect the number of weeds.
6

Which statement about these methods is true?

A
Methods 1 and 2 are both experiments because both use the new fertilizer.
B
Method 2 is an experiment because the plots are randomly assigned a fertilizer.
C
Method 1 is an experiment because the farm uses the new fertilizer.
D
Method 2 is an experiment because there are 16 different plots used.
7

Which statement about these methods is true?

A
Method 1 is an observational study because it does not attempt to influence responses.
B
Method 2 is an observational study because it does not attempt to influence responses.
C
Method 2 is an observational study because it could include golfers from many golf courses.
D
Both methods are observational studies because they both collect information about shot length.
8

Which method describes an experiment?

A
Method 1 is an experiment because all volunteers receive coats with the new insulation.
B
Method 2 is an experiment because both groups report their satisfaction with the coats.
C
Method 2 is an experiment because volunteers are assigned one of the two insulation types.
D
Method 1 is an experiment because the volunteers’ satisfaction with the new insulation can be measured.
9

An article in a psychology journal claims that young students who play a musical instrument tend to have higher test scores on state math exams. Which statement most likely describes the relationship between playing an instrument and state math exam scores?

A
Students who have high math scores should be encouraged to play a musical instrument so they become proficient with music as well.
B
Students who play a musical instrument tend to excel in other skills, which may explain their higher math scores.
C
Students who do not play musical instruments do not have high scores on state math exams.
D
Playing a musical instrument causes a student to become better at solving math problems.
10

A researcher conducts an experiment using 10 loads of white shirts with similar stains. The loads are divided, and 5 of the loads are washed with name-brand detergent, while the other 5 are washed with store-brand detergent. Volunteers are asked to assess the cleanliness of the shirts. What are the experimental units in this setting?

A
the volunteers who assess the stains
B
the 10 loads of shirts
C
the types of detergent
D
the machines used to wash the shirts

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