Which describes a quasi-experimental design and how it differs from a randomized controlled trial?

Which describes a quasi-experimental design and how it differs from a randomized controlled trial?

• A. A design with random assignment of participants.
• B. A design with no control group.
• C. A design with non-random assignment or controls.
• D. A design with blinding and randomization.

Answer: (C)

Quasi-experimental designs estimate causal effects when random assignment isn’t feasible. The key feature is non-random assignment to the intervention or to comparison groups (or using non-equivalent control groups). Because groups aren’t created by chance, there can be preexisting differences that influence outcomes, so researchers use methods like matching, statistical controls, or interrupted time-series designs to try to account for those differences. This is what distinguishes quasi-experiments from randomized controlled trials, where participants are assigned to conditions by randomization, helping ensure groups are comparable at the start. Options that emphasize randomization or blinding reflect true randomized trials, while describing no control group can occur in some quasi-experiments but isn’t the defining trait. The essence of a quasi-experimental design is non-random assignment or non-equivalent controls, which is why that description is the best fit.

Quasi-experimental designs estimate causal effects when random assignment isn’t feasible. The key feature is non-random assignment to the intervention or to comparison groups (or using non-equivalent control groups). Because groups aren’t created by chance, there can be preexisting differences that influence outcomes, so researchers use methods like matching, statistical controls, or interrupted time-series designs to try to account for those differences. This is what distinguishes quasi-experiments from randomized controlled trials, where participants are assigned to conditions by randomization, helping ensure groups are comparable at the start. Options that emphasize randomization or blinding reflect true randomized trials, while describing no control group can occur in some quasi-experiments but isn’t the defining trait. The essence of a quasi-experimental design is non-random assignment or non-equivalent controls, which is why that description is the best fit.