In a correlational design, researchers __________.

Correct Answer: A

Rationale: In a correlational design, researchers gather information on individuals without altering their experiences. Correlational studies examine the relationship between two or more variables without any manipulation or control by the researchers. The researchers simply observe and measure the variables of interest without intervening in any way. Choices B, C, and D are incorrect because they describe aspects related to experimental designs rather than correlational designs. In an experimental design, researchers manipulate variables, assign participants to different treatment conditions, and control changes in the independent variable, which is not the case in correlational studies.

Correct Answer: B

Rationale: By using random assignment of participants to treatment conditions, investigators increase the chances that participants' characteristics will be equally distributed across treatment groups. Random assignment helps reduce the likelihood of bias in the selection process and ensures that any differences between groups are due to the treatment and not pre-existing group differences. Sequential, systematic, and correlational assignment methods do not provide the same level of assurance in distributing participants' characteristics equally across treatment groups.

Correct Answer: C

Rationale: The correct answer is C: longitudinal. In a longitudinal design, participants are followed and studied over an extended period, allowing researchers to observe changes and continuity in development as individuals age. This design is crucial for understanding how individuals grow and change over time. Cross-sectional studies (Choice A) involve comparing different groups at the same time point, while experimental studies (Choice B) involve manipulating variables to observe their effects. Correlational studies (Choice D) examine relationships between variables but do not involve studying participants over time.

Correct Answer: D

Rationale: The concern Professor Higgins has regarding the findings of the longitudinal study is related to cohort effects. Cohort effects occur when a specific group of individuals experience a common event or circumstance that could influence the results of a study. In this case, the participants witnessing the terrorist attacks on the World Trade Center could have had a significant impact on their development and mental health outcomes, leading to cohort effects observed in the study. Choice A, 'practice,' is incorrect as it refers to the repeated performance of an activity to improve skill. Choice B, 'cross-sectional,' is incorrect as it involves data collection at a single point in time. Choice C, 'dropout,' is incorrect as it refers to participants leaving a study prematurely.

Correct Answer: B

Rationale: A sequential design permits researchers to check if cohort effects are operating. This design involves combining cross-sectional and longitudinal research, allowing for the comparison of different cohorts at different ages. By using this approach, researchers can determine if developmental changes observed are due to age or generation-specific factors. Therefore, a sequential design is valuable in addressing the potential influence of cohort effects on developmental outcomes. Choices A, C, and D are incorrect because a sequential design does not neglect diversity in developmental outcomes, is not necessarily less efficient than a longitudinal design, and can make both cross-sectional and longitudinal comparisons.