Mark is a graduate student who is studying identity formation. he interviews a group of 5-year-olds, a group of 10-year-olds, and a group of 15-year-olds and asks them what they plan to be when they finish school. in this example, mark is using a research design.

cross-sectional      

Explanation:

Cross-sectional research design: It involves various group of people who shares few characteristics but differs in the variable of interest, such as educational background, ethnicity, and socioeconomic status. Researchers who study developmental psychology often use cross-sectional research studies.

Example: A researcher can collect cross-sectional data related to current diagnoses of lung cancer and past smoking habits.

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