Quasi-experimental designs differ from true experiments in that they typically lack what elements?

Quasi-experimental designs differ from true experiments in that they typically lack what elements?

• A. Random sampling and manipulation
• B. Randomization and a control/comparison group
• C. Before-and-after measures
• D. A continuous outcome

Answer: (B)

The essential idea is about internal validity: true experiments secure causal inference by randomly assigning participants to conditions and including a control or comparison group. This combination helps ensure the groups are equivalent at the start and that any observed effect can be attributed to the intervention rather than other factors. Quasi-experimental designs, however, typically lack one or both of these features—random assignment and a distinct control/comparison group. Without randomization, groups may differ in important ways before the intervention, and without a control group, there’s no baseline for comparison to rule out alternative explanations. That’s why the elements missing in quasi-experiments are randomization and a control/comparison group.

The essential idea is about internal validity: true experiments secure causal inference by randomly assigning participants to conditions and including a control or comparison group. This combination helps ensure the groups are equivalent at the start and that any observed effect can be attributed to the intervention rather than other factors. Quasi-experimental designs, however, typically lack one or both of these features—random assignment and a distinct control/comparison group. Without randomization, groups may differ in important ways before the intervention, and without a control group, there’s no baseline for comparison to rule out alternative explanations. That’s why the elements missing in quasi-experiments are randomization and a control/comparison group.