Means that everyone in the population has the same likelihood of being asked to participate in the study.

operationalizing

placebo effect

random assignment

random sampling

Random sampling

Explanation:

A random sample is a subset of individuals (the sample) selected entirely at random from a larger set (the population) by a process that ensures that:

All individuals in the population are equally likely to be chosen for the sample; and Each possible subset of individuals (sample) is just as likely to be chosen as any other subset of individuals.

If we want to be more rigorous we can say that "A simple random sample is any size sample drawn from any size population such that every possible size sample is just as likely to be selected".