What is the term for a portion that fairly represents a population by giving each member an equal chance of inclusion?

The term for a portion that fairly represents a population by giving each member an equal chance of inclusion is random sampling. This method is essential in research because it minimizes bias and ensures that the sample reflects the diversity of the entire population. When every individual has an equal probability of being selected, it enhances the validity and generalizability of the results.

In contrast, sampling bias occurs when certain members of the population have a higher probability of being included than others, leading to skewed results. Systematic sampling involves selecting members of a population based on a fixed interval, which may introduce bias if the interval coincides with patterns in the population. Stratified sampling divides the population into subgroups and samples from each, intending to ensure representation, but it does not provide every member with an equal chance of selection within those strata. Thus, random sampling remains the most robust method for obtaining a representative sample.