Representative samples are only a concern in quantitative studies rooted in a positivistic research approach. Qualitative studies rooted in interpretivism usually do not attempt to generalize their findings to a population
The advantages of sampling over census studies are less compelling when the population is small and the variability within the population high. Two conditions are appropriate for a census study: when the population is small and when the elements are quite different from each other
The numerical descriptors that describe samples may be expected to differ from those that describe populations because of random fluctuations inherent in the sampling process
The members of a sample are selected on a probability basis or by another means, ensuring each population element has a known non-zero chance of selection
Simple random sampling is often impractical as it requires a population list that is often not available, fails to use all the information about a population, and may be expensive to implement
The population is divided into several mutually exclusive sub-populations or strata, and the sample is constrained to include elements from each segment