Ed Daly: "Single-Case Experimental Designs: Can You Really Conduct a True Experiment With So Few Participants?"

Ed Daly, Ph.D.

Professor, Educational Psychology
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In an age in which “evidence-based practice” has become the standard for virtually every professional field, why does it seem that little evidence-based practice occurs in the real world?

Looking for answers, scientists often accuse practitioners of not applying the results of their research, and practitioners retort that scientists do not generate useful research that addresses the complexities of the environments in which they work. Unfortunately, both sides are correct.

Single-case experimental designs represent a methodological approach that prioritizes the intensive analysis of the individual over time through repeated measures and strategic comparisons that allow the investigator to isolate and control naturalistic setting variables. Rather than deal with variability through statistical analyses, single-case researchers purposefully track down sources of variability within the individual over time to establish experimental control through both direct and systematic replications that expand our knowledge base.

By graphically displaying the data over time, the investigator dynamically interacts with the subject matter to pursue both questions of experimental control and corrections to the course through response-guided experimentation. Even when generalizations from prior research appear tenuous, single-case researchers also have at their disposal a methodology that can be used in natural settings with real clients to eliminate the science-to-practice gap that has held us all back for far too long.