Question 1

The problem of external validity refers to the generalizability of results.

Accepted Answer

The problem of external validity refers to the ability to generalize research findings beyond the specific sample and setting used in the study.

Question 2

Explain the elements of the class experimental design.Is this design especially useful in dealing with causal relationships? If yes,why? If not,why?

Accepted Answer

The answer of Explain the elements of the class experimental...

Question 3

Explain what is meant by internal and external validity.

Accepted Answer

The answer of Explain what is meant by internal and...

Question 4

Time series designs with many measurement points control for statistical regression.

Accepted Answer

Time series designs with many measurement points have autocorrelation or dependence between observations, and control for statistical regression, which is the tendency of extreme values to regress towards the mean in subsequent measurements.

Question 5

Case-control designs have more controls for threats to validity than do most other designs for evaluating programs or practice.

Accepted Answer

Case-control designs are observational and retrospective, which can introduce biases and confounding variables, making them less robust in controlling threats to validity compared to experimental designs.

Question 6

Random assignment to experimental and control groups controls for research reactivity.

Accepted Answer

Random assignment controls for confounding variables by ensuring that each participant has an equal chance of being assigned to any group, thus equalizing the groups on average. Research reactivity, however, refers to changes in participants' behavior due to their awareness of being observed, which is not directly addressed by random assignment.

Question 7

What differentiates experimental from pre-experimental designs? Give an illustration of a situation in which an experimental design would be preferred and one in which a pre-experimental design would be acceptable.

Accepted Answer

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Question 8

Professor Rose was asked to design an experiment to test whether obese people would lose weight on a new diet plan.Professor Rose was not a methodologist.Rose asked for your help.You immediately told Rose that the selected design would have to be sensitive to the issues of statistical regression,diffusion or imitation of treatment,compensatory rivalry,and demoralization.Rose said,"I don't understand." Explain these issues to Rose.Suggest and explain a design that would control for these problems.

Accepted Answer

The answer of Professor Rose was asked to design an...

Question 9

Without using appropriate experimental and control groups,extraneous events in subjects' lives can make history a threat to internal validity,even if those events are of no historical importance to people in general.

Accepted Answer

Without appropriate experimental and control groups, it is difficult to isolate the effects of the independent variable from other external factors, such as extraneous events in subjects' lives. These events can create confounding variables, which undermine the internal validity of the study by making it unclear whether the observed changes are due to the independent variable or some other factor. Even if these events are not historically significant, they can still have an impact on the results of the study, which is why it is important to control for them through proper experimental design.

Question 10

The one-group pretest-posttest design controls for passage of time.

Accepted Answer

The one-group pretest-posttest design does not control for the passage of time because it lacks a control group to compare against, making it difficult to determine if changes are due to the intervention or simply the passage of time.

Question 11

Studies that assign subjects to intervention groups on the basis of their extreme scores are vulnerable to regression toward the mean.

Accepted Answer

This is true because when subjects are selected based on extreme scores, their scores are likely to be less extreme on the second measurement due to natural variability and chance. This is called regression toward the mean, and can result in an overestimation of the effectiveness of the intervention.

Question 12

Discuss how attrition can affect the validity of an experiment and describe steps to minimize attrition.

Accepted Answer

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Question 13

The effectiveness of randomization in experimentation is affected by the number of participants involved.

Accepted Answer

The larger the number of participants, the more effective randomization becomes in ensuring that the sample is representative of the population and reducing the likelihood of bias. A smaller sample size may have a greater chance of producing results that are not reflective of the larger population.

Question 14

The classic experiment with random assignment of participants controls for measurement bias.

Accepted Answer

Random assignment controls for selection bias, not measurement bias. Measurement bias is related to how data is collected or measured, not how participants are assigned to groups.

Question 15

Quasi-experiments using nonequivalent comparison groups without random assignment can be credible,assuming that the comparability of the experimental and comparison groups is plausible-especially if the researcher provides substantial evidence of that comparability.

Accepted Answer

The statement is true. Quasi-experiments using nonequivalent comparison groups without random assignment can still be credible as long as the comparability of the experimental and comparison groups is plausible, and the researcher provides substantial evidence of that comparability.

Question 16

Time series designs with many measurement points control for maturation.

Accepted Answer

Time series designs with many measurement points control for maturation through repeated measures of the outcome variable over time, allowing for changes in the outcome to be attributed to the intervention rather than natural developmental processes.

Question 17

Attrition effects are automatically controlled when participants are assigned randomly to experimental and control groups.

Accepted Answer

Random assignment helps to ensure that groups are equivalent at the start of the experiment, but it does not control for attrition effects (loss of participants) that occur after the experiment begins. Attrition can still introduce bias if the reasons for dropout differ systematically between the groups.

Question 18

Discuss the advantages and disadvantages of cross-sectional studies and the case control design.

Accepted Answer

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Quiz 12: Experiments and Quasi-Experiments