To measure whether older people are calmer than younger people, a researcher gives 20-year-olds, 40-year-olds, and 60-year-olds a questionnaire. this research technique is called a(n): a. correlational study. b. longitudinal study. c. experiment. d. cross-sectional study.

d. cross-sectional study

Explanation:

In research, a cross-sectional study consists of a gathering of data from a population or a subset of the population we want to investigate at an specific point of time. In other words, the data will give us an idea of what's happening within a group in a particular moment in time.

In this example, the researcher gives 20-year-olds, 40-year-olds, and 60-year-olds a questionnaire. He wants to know if older people are calmer than younger ones. We can see that he wants to know what's happening within this groups (the 20 year-olds, the 40's and the 60's) during this particular time of their life and therefore determine if the 60 year-olds are calmer. Therefore this is an example of cross-sectional study.

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