A researcher examined the effects of mood on aggression in an experiment. She decided to see how receiving an insult or a compliment affects aggression, and she measured aggression by having participants administer small shocks to another participant. The researcher found that participants in the insult condition were more aggressive than those in the compliment condition. One of her colleagues reads about this research and voices concern that people in the insult condition may have been more naturally aggressive than people in the compliment condition, causing the differences observed by the researcher. This concern about preexisting differences between participants in the two conditions would only be valid if participants were not

Question

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Random assignment to conditions is crucial in experimental research to ensure that any preexisting differences among participants are evenly distributed across all conditions, thereby minimizing their potential impact on the outcome. If participants were not randomly assigned, it could lead to groups that are not equivalent at the start of the experiment, which might explain differences in aggression due to preexisting characteristics rather than the experimental manipulation (receiving an insult or a compliment).

A Researcher Examined the Effects of Mood on Aggression in an Experiment