A review of the non-equivalent control group post-test-only design.

BACKGROUND: Quantitative research designs are broadly classified as either experimental or quasi-experimental. The main distinguishing feature of the quasi-experiment is the manipulation of the independent variable without randomisation. When randomisation or use of a control group is unfeasible, a researcher can choose from a range of quasi-experimental designs.

AIM: To present the features of the quasi-experimental 'non-equivalent control group post-test-only' design, which aims to demonstrate causality between an intervention and an outcome.

DISCUSSION: This paper provides an overview of the non-equivalent control group post-test-only design in terms of its design features, applications and statistical analysis, as well as its advantages and disadvantages.

CONCLUSION: The non-equivalent control group post-test-only design can be used in natural settings, where randomisation cannot be conducted for ethical or practical reasons. Although the design is less complex than some other designs, with low error propagation, it is vulnerable to threats to internal validity.