What distinguishes quasi-experimental design from true experimental design?

Quasi-experimental design is characterized primarily by the lack of random assignment of participants to different groups. In true experimental designs, researchers randomly assign participants to control or experimental groups, which helps to ensure that any differences observed between the groups can be attributed to the intervention being tested rather than other confounding variables. This randomization creates groups that are statistically similar, reducing bias and enhancing the ability to infer causality.

In contrast, the absence of random assignment in quasi-experimental designs introduces potential biases because the groups may differ in ways that affect the outcome, making it more challenging to establish definitive causal relationships. While quasi-experimental designs can still provide valuable insights, particularly in settings where randomization is not feasible or ethical, they require careful consideration of confounding factors and may limit the generalizability of the findings due to the potential for selection bias.

The other options do not accurately reflect the fundamental distinction that sets quasi-experimental designs apart from true experimental designs. For instance, having diverse participant backgrounds, larger sample sizes, or better control of variables is not specifically related to the classification of quasi-experimental versus true experimental designs. These aspects can vary in both types of designs depending on the research context and methods employed.