A quasi-experiment is a type of research design that aims to evaluate the effect of an intervention or treatment without random assignment of participants. Instead of randomly assigning subjects to different groups, researchers use existing groups or conditions, which can lead to potential biases. This design is often used in real-world settings where randomization is impractical or unethical. Quasi-experiments are commonly found in fields like education, psychology, and public health. For example, a study examining the impact of a new teaching method in a classroom might compare test scores of students in one school to those in another school using traditional methods, without randomly assigning students to each group.