What is the main difference between quasi-experimental and experimental study designs?

The main difference between quasi-experimental and experimental study designs is the presence of random assignment of participants in experimental designs. In experimental studies, researchers actively manipulate one or more independent variables while randomly assigning participants to either the treatment group or a control group. This randomization helps to ensure that any differences observed in the outcomes can be attributed to the intervention itself rather than to pre-existing differences between participants.

In contrast, quasi-experimental designs do not incorporate random assignment. Instead, they may use existing groups or allow for participant selection based on certain criteria, which can lead to potential biases in how the groups are formed. Without random assignment, it becomes more challenging to establish a causal relationship between the independent and dependent variables, as other confounding factors may influence the results.

The other options, while related to study designs, do not accurately capture the defining difference between quasi-experimental and experimental designs. For example, the mention of comparing groups is applicable to both types of designs, not a distinguishing feature. The manipulation of multiple independent variables may occur in both designs and does not clarify their fundamental difference. Additionally, the statement regarding the use of experimental designs only for drug trials is overly restrictive and inaccurate, as experimental designs are utilized across various fields, including education, psychology,