Statistics How To

Sampling Design

Sampling >

Sampling design is a mathematical function that gives you the probability of any given sample being drawn.

Since sampling is the foundation of nearly every research project, the study of sampling design is a crucial part of statistics, and is often a one or two semester course. It involves not only learning how to derive the probability functions which describe a given sampling method but also understanding how to design a best-fit sampling method for a real life situation.

Examples of Sampling Design

Sampling design can be very simple or very complex. In the simplest, one stage sample design where there is no explicit stratification and a member of the population is chosen at random, each unit has the probability


of being in the sample, where:

  • n is the total number of units to be sampled,
  • N is number of units in the total population.

Other types of design include:

  • Systematic sample: all members of a population are listed in order and samples are chosen at defined intervals
  • Stratified sample: the population is first divided into strata and then samples are randomly selected from the strata (for example, divide a population between men and women, then randomly select a given number of men and a given number of women)
  • Cluster strata: a population is divided into clusters and first clusters are randomly selected, then random members of the selected clusters are sampled. (for instance, first randomly select a number of classes, then, from the class lists of those classes, randomly sample a number of students)

Each of these have their own sampling design function. The sampling method chosen will depend on the situation and priorities of the researcher. Sometimes, non-probability sampling methods will be chosen; for example, convenience sampling, where the sample is simply those easily reached and observed. Unlike systematic, stratified, or cluster sampling, these types of sampling cannot be easily described by a function.


Mohadjer, Krenzke, & Van de Kerckhove. Technical Report. Chapter 4. Survey of Adult Skills (PIAAC), OECD.
Retrieved from on September 3, 2018

Maastricht University. Course Catalogue. Retrieved from on September 3, 2018.

Raymo, Jim. Sample Design. Sociology 357 Class Notes.
Retrieved from on September 3, 2018.


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