Quasi-experimental designs are research methods that aim to evaluate the effects of an intervention or treatment without random assignment of participants. These designs often use existing groups, such as classrooms or communities, to compare outcomes. This approach allows researchers to study real-world settings while still attempting to establish causal relationships. While quasi-experimental designs can provide valuable insights, they may be more susceptible to biases than true experiments. Researchers must carefully consider confounding variables and use statistical techniques to control for these factors. Common examples include pretest-posttest designs and non-equivalent control groups.