What is the primary feature that differentiates a quasi-experimental design from a true experimental design?

The key distinction that sets quasi-experimental designs apart from true experimental designs lies in the use of sampling techniques. Specifically, quasi-experimental designs typically rely on convenience sampling rather than random sampling to select subjects. In random sampling, participants are selected in such a way that every individual has an equal chance of being included, which helps to minimize bias and ensures that groups are comparable at baseline.

Quasi-experimental designs, on the other hand, often use existing groups or other non-randomized methods to recruit participants. This approach is practical and sometimes necessary, especially in real-world settings where random assignment may be infeasible or unethical. However, this method can introduce confounding variables and potential biases, ultimately impacting the validity of the findings.

While observational studies can involve various research strategies, the defining characteristic of quasi-experimental designs is the lack of random assignment. Regarding the classification as a survey, it’s important to note that surveys can be part of any study design but do not define the nature of the experimental design itself. Lastly, every quasi-experimental design does indeed include intervention groups; what distinguishes these designs is the method of assigning participants to those groups.