The simple definition of Quasi experimental design is a form of experimental research used extensively in the social sciences and psychology. types of quasi experimental and experimental designs. All offer some advantages over the simple before and after design, because some of the threats to internal validity are eliminated.
Quasi- experimental Design retrospective ex Post Facto Design: Ex post facto means “after the fact”. Experimental Design in Research There are two groups, the exposure group and the comparison group. The process of “constructing” comparable exposure and comparison groups is called “matching”. The subjects are already naturally divided like that. However, the experimenter selects the relevant subjects according to the nature of the research.
Prospective Design: This design is similar to the retrospective design, except that in a prospective design, variations in the independent variable are measured as they occur, rather than retrospectively. Researchers are equally careful in interpreting the prospective and retrospective quasi- experiments. In neither case, the subjects are randomly assigned to the exposure and the control groups. Generally, prospective designs are more persuasive than retrospective designs, especially when the independent variable occurred long ago
Time series Design: This design is mainly concerned with observing whether the values of the dependent variable change in apparent response to changes in an independent variable.
Examples of Quasi Experimentation
Twin studies investigate different aspects of behavior and mental processes of twins, whether identical or fraternal. The studies on identical twins reared apart have generated very significant results. They have shown amazing similarities as well as differences among such twins.
Most people have one set of parents. However 1% of the infants born in western countries every year are adopted at or near by persons unrelated to them. Such children have two sets of parents: parents who rear them and those who give them their genes. Social scientists have used this to help determine, with fascinating results, how much influence genetic factors and family environment have over behavior. Like twin studies, adoption studies suggested that many human behaviors are genetically influenced. That is why the nature- nurture issue is always remaining controversial.
Applied Research: Single- Case Research Designs
• A type of research in which a single case is focused upon and studied.
• This approach is employed in rarely occurring cases.