Experimental designs and true experimental designs both aim to establish causal relationships by manipulating independent variables and measuring their effects on dependent variables. However, the critical distinction between the two lies in the method of participant assignment to treatment groups.
In true experimental designs, participants are randomly assigned to groups, which helps ensure that any differences observed between the groups can be attributed to the manipulation of the independent variable, rather than pre-existing differences among participants. This random assignment controls for confounding variables and enhances the internal validity of the study.
On the other hand, experimental designs that lack random assignment are often referred to as quasi-experimental designs. In these designs, participants may be assigned to groups based on certain characteristics, self-selection, or other non-random methods. While these designs still involve manipulation of an independent variable, the lack of random assignment can introduce potential biases and confounding variables, making it more challenging to draw causal conclusions.
In summary, the key difference is that true experimental designs use random assignment to control for confounding factors, while quasi-experimental designs do not, which can impact the validity of the findings.
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