2.3 Random allocation vs random sampling

Random sampling and random allocation are two different concepts (Fig. 2.4), that serve two different purposes, but are often confused:

  • Random sampling allows results to be generalised to a larger population, and impacts external validity. It concerns how the sample is found to study.
  • Random allocation tries to eliminate confounding issues, by evening-out possible confounders across treatment groups. Random allocation of treatments helps establish cause-and-effect, and impacts internal validity. It concerns how the members of the chosen sample get the treatments.
Comparing random allocation and random sampling

Figure 2.4: Comparing random allocation and random sampling

This material was written by Peter K. Dunn and adapted by Amanda J. Shaker. Unless otherwise stated, material within this work is licensed under a Creative Commons Attribution-Non Commercial-Share Alike License CC BY-NC-SA