<P> In design of experiments, single - subject design or single - case research design is a research design most often used in applied fields of psychology, education, and human behavior in which the subject serves as his / her own control, rather than using another individual / group . Researchers use single - subject design because these designs are sensitive to individual organism differences vs group designs which are sensitive to averages of groups . Often there will be large numbers of subjects in a research study using single - subject design, however--because the subject serves as their own control, this is still a single - subject design . These designs are used primarily to evaluate the effect of a variety of interventions in applied research . </P> <P> The following are requirements of single - subject designs: </P> <Ul> <Li> Continuous assessment: The behavior of the individual is observed repeatedly over the course of the intervention . This ensures that any treatment effects are observed long enough to convince the scientist that the treatment produces a lasting effect . </Li> <Li> Baseline assessment: Before the treatment is implemented, the researcher is to look for behavioral trends . If a treatment reverses a baseline trend (e.g., things were getting worse as time went on in the baseline but the treatment reversed this trend) then this is powerful evidence suggesting (though not proving) a treatment effect . </Li> <Li> Variability in data: Because behavior is assessed repeatedly, the single - subject design allows the researcher to see how consistently the treatment changes behavior over time . Large - group statistical designs do not typically provide this information because repeated assessments are not usually taken and the behavior of individuals in the groups are not scrutinized; instead, group means are reported . </Li> </Ul> <Li> Continuous assessment: The behavior of the individual is observed repeatedly over the course of the intervention . This ensures that any treatment effects are observed long enough to convince the scientist that the treatment produces a lasting effect . </Li>

Design and interpretation of studies of single subjects