What does random assignment in a study achieve?

Random assignment in a study primarily serves to give all participants an equal chance of being assigned to any group. This process is crucial in experimental research because it helps ensure that each group is likely to be comparable at the start of the experiment. By randomly assigning participants, the researcher minimizes the influence of pre-existing differences among participants that could affect the experimental outcome. This method enhances the internal validity of an experiment, allowing researchers to attribute any differences in outcomes between the groups directly to the treatment or intervention being tested, rather than to other extraneous variables.

While random assignment can also contribute to controlling extraneous variables, its primary goal is to ensure that any individual differences among participants do not skew the results of the study. This is distinct from factors such as participant comfort or ethical concerns, which are important but are not the main objectives of random assignment.