Sampling the entire population of interest often requires more resources (time, money) than the researcher has at their disposal. As a result, samples of the population are utilized. There are various strategies used to create samples, each of which is designed to meet certain criteria. A brief overview will be provided, along with links to online resources for further information.
While it is often impossible to survey an entire population, researchers should not arbitrarily select the size of their samples. Factors such as the degree of variability in the population, the analysis the results will be subject to, or the degree of accuracy required, are critical to determining sample size.