What type of sample allows each member of a population an equal chance of inclusion?

A random sample ensures that every member of the population has an equal chance of being selected for the study. This method is critical in research because it eliminates selection bias, allowing for a more accurate representation of the population as a whole. The randomness helps to ensure that the results can be generalized beyond the sample, leading to more valid conclusions.

In contrast, a purposive sample selectively includes participants based on specific characteristics, which does not provide each member of the population an equal chance of inclusion. A convenience sample is based on selecting individuals who are easiest to access, which can lead to significant biases. A stratified sample divides the population into distinct subgroups and then samples from those groups, but not every individual has an equal chance of being selected overall. Thus, while these other sampling methods can be useful in certain contexts, they do not provide the equal opportunity for selection that a random sample does.