There are two primary types of research designs: experimental and nonexperimental. Experimental designs are those in which the researcher has complete control over the independent and dependent variables. These types of studies are often used in scientific settings where the goal is to determine cause and effect relationships. In contrast, nonexperimental designs are less controlled, and therefore provide less conclusive findings. However, they can be useful for exploratory research or in situations where conducting an experiment would be impractical (Leventhal & Dupéré, 2019).
One example of an experimental design would be a laboratory study in which participants are assigned to different conditions (e.g., receiving a treatment or not) and their responses are measured. The study,” Impact of tart cherry juice on systolic blood pressure and low-density lipoprotein cholesterol in older adults: a randomized controlled trial” by Chai et al., (2018) is an example of experimental study design. This type of study allows the researcher to isolate the effects of the independent and the dependent variables. On the other hand, the study, “Association between stress and hypertension among adults more than 30 years” by Bhelkar et al., (2018) is an example of nonexperimental study design.
In nonexperimental research design, there are three main levels of control: (1) experimental, (2) quasi-experimental, and (3) non-experimental. In experimental research design, the researcher has complete control over all aspects of the study. The researcher manipulates one or more independent variables and measures the impact on one or more dependent variables (Ross & Grant, 2019). In quasi-experimental research design, the researcher does not have complete control over all aspects of the study but does have some degree of control over key elements that could impact results (Chiang et al., 2020). For example, the researcher might select a comparison group that is not randomly assigned to ensure that groups are matched on important characteristics.
Chiang, I. C. A., Jhangiani, R. S., & Price, P. C. (2020). Overview of nonexperimental research. Research Methods in Psychology-2nd Canadian Edition. https://opentextbc.ca/researchmethods/chapter/overview-of-nonexperimental-research/
Leventhal, T., & Dupéré, V. (2019). Neighborhood effects on children’s development in experimental and nonexperimental research. Annual review of developmental psychology, 1, 149-176. https://www.annualreviews.org/doi/abs/10.1146/annurev-devpsych-121318-085221
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