What do quasi-experimental designs lack compared to randomized controlled trials?

Quasi-experimental designs are characterized by the absence of randomization in the assignment of participants to treatment or control groups, which is a defining feature of randomized controlled trials (RCTs). This lack of randomization can introduce potential biases, as the groups may differ in ways that affect the outcomes of the intervention being studied.

Additionally, while quasi-experimental designs may include a control group, the lack of randomization means that factors influencing the results may not be evenly distributed across the groups being compared. In contrast, RCTs are designed to minimize these confounding variables by randomly assigning participants, which enhances the internal validity of the study. Therefore, the main distinction lies in how participants are assigned to their respective groups, making randomization critical for the strength and reliability of causal inferences drawn from RCTs.

The other options, while they may pertain to aspects of study design, do not specifically highlight the primary difference that defines quasi-experimental designs in comparison to randomized controlled trials.