Research is broadly divided into two categories: qualitative and quantitative. Within each of those categories are multiple designs and methods. Among the quantitative methodologies are quasi-experimental designs.

Quasi- experimental designs are similar to experimental designs. They are designs in which a controlled experiment is carried out in order to determine if there exist statistical similarities within or between groups of subjects. The process requires a pre-test and a post-test of the subjects, and the application of a treatment or condition change.  A control group must also be established to make a statistical comparison that helps determine the effectiveness of the treatment or condition applied.

However, there are differences between experimental and quasi-experimental designs. The most significant of these differences is that quasi-experimental designs do not use random assignment of participants to the experimental and control groups. Since the groups are not randomly assigned, they may not be equivalent. Thus, the researcher must be aware of potential issues with internal validity. The result of these issues may be, at the worst, a false conclusion that claims the conditions did or did not have a significant effect when in truth the opposite was true.

Experiments can be carried out using independent samples or within-subjects designs. The same statistical models used for pure experimental designs are applicable to quasi-experimental designs as well. These models include the one-sample paired sample, or independent-sample t-test; one-way or repeated measures analysis of variance (ANOVA); Chi-square test; and non-parametric tests. However, interpretation of results must be carefully considered given the concerns regarding internal validity as mentioned above. Learners should collaborate closely with their assigned methodologists when conducting quasi-experimental research and performing the statistical analysis of the study.

Quasi-experimental design is but one form of research design that is suitable and meaningful for dissertation research. Additional designs will be reviewed later in this series. In all cases, learners are advised to have relevant conversations with their dissertation committee and their methodologist and chair in particular to determine the best design to address the research questions of the proposed dissertation study.