Answer to Question 1
C
Feedback:
Correlational studies are susceptible to faulty interpretation because groups being compared have formed through self-selection (also called selection bias). When researchers study the effect of a cause they cannot manipulate, they use correlational designs that examine relationships between variables. A correlation is an interrelationship or association between two variables, that is, a tendency for variation in one variable to be related to variation in another. Correlations can be detected through statistical analyses.
Answer to Question 2
B
Feedback:
In pretest-posttest designs, data are collected both before the intervention (at baseline) and after it (outcome). The control group can undergo various conditions, including no treatment; an alternative treatment; a placebo or pseudo intervention; standard treatment at different treatment doses; or a wait-list condition. In the Hawthorne effect, various environmental conditions vary to determine their effect on worker productivity. Blinding is another means of controlling external sources of bias. Matching is deliberately making groups comparable on some extraneous variables. Longitudinal studies are typically expensive, time-consuming, and subject to the risk of attrition (loss of participants over time). Mortality is the threat that arises from attrition in groups being compared. If different kinds of people remain in the study in one group versus another, then these differences, rather than the independent variable, could account for group differences in outcomes.