What is the term for the selection procedure ensuring all participants have an equal chance of being in either group?

The term that specifically refers to the selection procedure ensuring all participants have an equal chance of being assigned to either group within an experiment is random allocation. This process is crucial in experimental design because it minimizes bias and ensures that any differences observed between groups are likely due to the independent variable being manipulated, rather than pre-existing differences among participants.

Random allocation helps to create equivalent groups in terms of characteristics such as age, gender, socioeconomic status, and other variables that might affect the results. This enhances the internal validity of the experiment. In contrast, random sampling refers to how participants are chosen from a larger population to participate in the study, while repeated measures design involves using the same participants across different conditions, and stratified sampling focuses on ensuring that specific subgroups are represented in the sample.