What does random assignment in experimental research help to ensure?

Random assignment in experimental research is crucial because it ensures that each participant has an equal chance of being assigned to any of the treatment or control groups. This process plays a vital role in enhancing the internal validity of a study by minimizing selection bias. When participants are randomly assigned, it helps create comparable groups that are similar in characteristics, thereby allowing researchers to make more reliable conclusions about the effects of the treatment or intervention being studied.

By randomizing the assignment, the researchers are less likely to have pre-existing differences between the groups that could influence the outcome of the experiment. Therefore, it allows for a more accurate assessment of the causal relationship between the independent variable and the dependent variable. The randomization process is fundamental to experimental design, as it directly contributes to the effectiveness of the research findings by strengthening the argument that observed effects are due to the treatment rather than other factors.