Quasi experimental lack of randomisation – UGC NET Question

A quasi-experimental design resembles a true experiment in that the researcher introduces an intervention or treatment and measures its effect on an outcome, but it lacks random assignment of participants to conditions. Groups may be pre-existing intact classes or institutions, which can introduce selection biases. Researchers often use statistical controls or matching to reduce these threats. Because the stem describes manipulation of an independent variable without random assignment, quasi-experimental design is the correct term.

Option A:
Experimental design includes both manipulation of independent variables and the random assignment of participants to treatment and control groups, which allows strong causal inferences. The absence of randomisation in the stem makes experimental design an inaccurate label in this case.

Option B:
Ex post facto design studies differences that already exist without manipulating variables, so it is non-experimental; the researcher only observes and tries to infer possible causes from existing conditions. The stem, however, explicitly mentions manipulation of the independent variable, which does not occur in ex post facto designs.

Option C:
Correlational design examines the relationships between variables without manipulating them, using statistical associations to describe and sometimes predict outcomes. It does not meet the criterion of introducing a treatment or intervention as stated in the stem. Therefore, correlational design is not the best completion here.

Option D:
Quasi-experimental designs are common in educational and social settings where random assignment is impractical or unethical, yet some level of control and manipulation is still feasible. They provide more tentative causal evidence than true experiments but are stronger than purely observational studies, matching the description in the question.