Populations and Samples
David M. McEvoy · 2018
This chapter explores established methods used to draw representative samples from a given population. A good sample is one that is a close representation of the larger population of interest. Achieving an unbiased, representative sample requires some degree of randomization. In a simple random sample, every unit in the population has the same chance of being included in the sample. Stratified sampling method leads to a closer estimate of the population survival rate. Another approach to stratified sampling is to conduct a simple random sample and then weigh the data to reflect the percentages in each stratum. Systematic sampling is the approach of choosing every kth item from a sequence or a list. Cluster sampling, another approach, is very similar to stratified sampling except that the strata are determined by geographic areas. All data-driven analysis requires a clear definition of the target population.