Larry conducts an experiment with groups randomly assigned to one of three conditions: (1) writing about traumatic events, (2) writing about happy events, OR (3) writing about neutral events. Larry then measures the number of visits each participant makes to the health center over the next six months. Larry gives the participants a pretest regarding their health visits prior to the study so that he can create sets of participants who are equivalent on that variable. In this design, Larry has used sets.

Matched set

Step-by-step explanation:

The type of set created here is a matched set where each of the participants are are grouped into variables equivalent to thwor number of visits which is based in prior investigation. The set of participant classed in to each group of neutral, traumatic and happy events are similar based on the grouping condition which is the number of health visits. Hence, when we have classes formed from equivalent behavior of characteristic based on the essence of an experiment, we have matched set.