AQA Psychology – Research Methods Practice Test

Random allocation means assigning participants to the different conditions by chance, so everyone has an equal chance of being in any group. This helps create comparable groups at the start of the experiment, reducing the influence of individual differences on the results and strengthening internal validity. It avoids self-selection or bias from pretest-based assignment, which can distort cause-and-effect conclusions. Choosing a condition based on preference, or assigning based on pretest scores, or deliberately balancing groups by the researcher without chance, all introduce systematic differences that can confound results.