Answer to Question 1
D
Feedback:
Techniques for controlling subject characteristics include homogeneity (restricting participants to reduce variability on confounding variables); matching (deliberately making groups comparable on some extraneous variables); statistical procedures; and randomizationthe most effective method because it controls all possible confounding variables without researchers having to identify them.
Answer to Question 2
B
Feedback:
External validity concerns inferences about whether relationships found for study participants might hold true for different people, conditions, and settingsin other words, generalizability. Using a homogeneous sample is easy, but one problem is limited generalizability. Indeed, one problem with this approach is that researchers may exclude people who are extremely ill or incapacitated, which means that the findings cannot be generalized to the very people who perhaps are most in need of interventions. Construct validity involves inferences from the particulars of the study to the higher-order constructs they are intended to represent. If studies contain construct errors, there is a risk that the evidence will be misleading. Intervention fidelity helps to avert biases and gives potential benefits a full opportunity to be realized. Internal validity is the extent to which it can be inferred that the independent variable is truly causing the outcome.
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