Question 1

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

Accepted 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.

Question 2

For Questions 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.)
-{BMD Narrative} Explain why it is not possible to conduct a randomized experiment in this situation.

Accepted 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.

Question 3

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

Accepted 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.

Question 4

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 above

Accepted Answer

The answer of Which of the following is implemented in...

Question 5

Experiments use __________ to reduce the effects of confounding variables and other sources of bias that are naturally present in observational studies.

Accepted Answer

The answer of Experiments use __________ to reduce the effects...

Question 6

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

Accepted Answer

All of the options mentioned (Matched-pairs, Repeated measures, Blocks) are experimental designs implemented to reduce known sources of natural variability in the response variable. This is done to ensure that any differences observed can be more confidently attributed to the explanatory variable rather than to other sources of variation. Matched-pairs involve pairing subjects based on similar characteristics, repeated measures involve measuring the same subjects under different conditions, and blocks involve grouping subjects based on an extraneous variable to control its effect on the outcome.

Question 7

For Questions 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.)
-{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.

Accepted Answer

The answer of For Questions use the following narrative
Narrative: BMD
A...

Question 8

What is one advantage of using a matched-pairs design in a randomized experiment?

Accepted Answer

The answer of What is one advantage of using a...

Question 9

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?

Accepted Answer

The answer of Using 20 pairs of identical twins to...

Question 10

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)It affects the response variable.
C)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

Accepted Answer

A confounding variable is related to the explanatory variable and affects the response variable, and its effect on the response variable cannot be separated from the effect of the explanatory variable on the response variable. Therefore, all of the statements above are properties of a confounding variable.

Question 11

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)A group that is used by researchers to monitor how the experiment is going.
C)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.

Accepted Answer

A control group is a group in an experiment that is handled identically to the treatment group(s) in all respects except that they do not receive the active treatment. This provides a baseline for comparison to determine the effectiveness of the treatment. Option A includes a confusing element "controlled to a greater extent" which is not needed in the definition. Option B is incorrect because a control group is not used to monitor how the experiment is going, but rather to provide a standard of comparison. Option D is incorrect as one of the options is correct.

Question 12

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.

Accepted Answer

Randomization in experiments involves randomly assigning the experimental units to different treatments. Option A is incorrect because random selection of units does not ensure random distribution of the units across treatments. Option C is also incorrect because the treatments should be predetermined before the experiment starts to avoid bias.

Question 13

A(n) __________ experiment is one in which neither the participant nor the researcher taking the measurements knows who had which treatment.

Accepted Answer

The answer of A(n) __________ experiment is one in which...

Question 14

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)The results cannot necessarily be extended to the larger population.
C)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.

Accepted Answer

Recruiting volunteers to participate in a randomized experiment may introduce volunteer bias, where the characteristics of the participants who volunteer may differ from those who do not, leading to results that may not be generalizable to the larger population.

Question 15

Which of the following describes an experiment?
A)Create differences in the explanatory variable and then examine the results.
B)Observe differences in the explanatory variable and then notice whether these are related to differences in the response variable.
C)Both a and b are experiments.
D)Neither a nor b are experiments

Accepted Answer

An experiment is a research design in which the researcher manipulates the explanatory variable and then measures the response variable. Choice A describes this process. Choice B describes an observational study, where the researcher simply observes differences in the explanatory variable and response variable without manipulating any variables.

Question 16

A(n) __________ variable is one that attempts to explain or is purported to cause (at least partially) differences in a(n) __________ variable.

Accepted Answer

The answer of A(n) __________ variable is one that attempts...

Question 17

For Questions 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.
-{Toy colors narrative} Is this study an observational study or an experiment?

Accepted Answer

The answer of For Questions use the following narrative
Narrative: Toy...

Question 18

Which of the following is not true about placebos?
A)Placebos can be very effective in producing a response.
B)Placebos are only useful if the subject is blind as to whether or not they receive one.
C)Participants assigned a placebo are part of the control group of an experiment.
D)All of the above are true statements.

Accepted Answer

The answer of Which of the following is not true...

Question 19

For Questions 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.
-{Toy colors narrative} What is the explanatory variable and what is the response variable?

Accepted Answer

The answer of For Questions use the following narrative
Narrative: Toy...

Question 20

One of the major advantages of an experiment over an observational study is that in an experiment, the researcher attempts to control for __________ variables.

Accepted Answer

The answer of One of the major advantages of an...

Quiz 5: Experiments and Observational Studies

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

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?

Experiments use __________ to reduce the effects of confounding variables and other sources of bias that are naturally present in observational studies.

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?

What is one advantage of using a matched-pairs design in a randomized experiment?

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?

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

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

What does randomization mean in terms of experiments?

A(n) __________ experiment is one in which neither the participant nor the researcher taking the measurements knows who had which treatment.

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

Which of the following describes an experiment?

A(n) variable is one that attempts to explain or is purported to cause (at least partially) differences in a(n) variable.

Which of the following is not true about placebos?

One of the major advantages of an experiment over an observational study is that in an experiment, the researcher attempts to control for __________ variables.