Which of the following is a method for ensuring that each participant has equal selection probability in research?

Random sampling is the method that ensures each participant has an equal probability of being selected for the study. This technique involves selecting participants from a larger population completely at random, which helps to minimize selection bias and enhances the generalizability of the results. By using this method, researchers can confidently claim that the sample accurately represents the population, as each individual has an equal chance of being included.

In contrast, quasi-experimental designs do not inherently offer equal selection probabilities since they often involve pre-existing groups rather than random selection. Snowball sampling relies on existing participants to recruit new ones, which can lead to a sample that is biased based on the social networks of those initial participants. Purposive sampling involves selecting participants based on specific characteristics or criteria, which inherently means not all individuals have an equal chance of selection. These alternatives do not meet the criteria for ensuring equal selection probability among participants.