The Research Designs decision tree will help with choosing the correct research design
1. Are you using random selection?
Random selection is the primary delineation between observational and experimental designs. When researchers pair random selection with random assignment, they are conducting a true experimental design, Experimental research designs can yield causal effects.
If random selection is used but random assignment is not ethical or feasible, then researchers are conducting quasi-experimental designs.
When random selection is not used at all, researchers are conducting observational research.
2. Are you using random assignment?
When paired with random selection, using random assignment of participants to treatment or control groups is part of conducting a randomized controlled trials (RCT) or an experimental design. And again, if researchers are using random selection, but not random assignment, then you are using quasi-experimental designs.
3. Have the outcomes occurred in the past or will they occur in the future?
If the outcomes already exist, then researchers are employing a retrospective design. All retrospective research designs are observational: Case series, case-control, cross-sectional, and retrospective cohort. These types of designs are very feasible for busy clinicians and researchers, because the data already exists!
f the outcomes occur in the future, researchers are using a prospective design. Prospective cohort designs are observational because participants are not chosen at random. Participants are assigned to a cohort and followed forward in time to understand the role of an exposure on future outcomes.
Research Designs decision tree
What type of research design will answer the research question?
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