Experimental Design
Practice the Experimental Design domain on demand, including single-case experimental design (SCED) graph-reading questions -- no need to wait for a mock exam to draw one.
About this domain
Experimental Design is one of the smallest domains on the BCBA exam (about 7% of questions) but it underlies almost everything else the exam tests: it is not possible to evaluate whether an intervention worked without knowing how a study demonstrates that it caused the change.
Behavior analysts favor single-case experimental designs (SCEDs) over group designs because each participant serves as their own control across repeated measurement over time. This lets a design verify an effect (the behavior changes when the intervention starts) and then replicate it (the same pattern shows up again), building confidence that the intervention -- not some outside factor -- caused the change. The four core SCEDs tested on the exam are reversal (ABAB), multiple baseline, multielement (alternating treatments), and changing criterion designs, each suited to different situations depending on whether a behavior can safely be reversed and how many behaviors, settings, or people are involved.
What the exam tests
- D.1 Distinguish between dependent and independent variables.
- D.2 Distinguish between internal and external validity.
- D.3 Identify threats to internal validity (e.g., history, maturation).
- D.4 Identify the defining features of single-case experimental designs (e.g., individuals serve as their own controls, repeated measures, prediction, verification, replication).
- D.5 Identify the relative strengths of single-case experimental designs and group designs.
- D.6 Critique and interpret data from single-case experimental designs.
- D.7 Distinguish among reversal, multiple-baseline, multielement, and changing-criterion designs.
- D.8 Identify rationales for conducting comparative, component, and parametric analyses.
- D.9 Apply single-case experimental designs.
Further reading
Cooper, J. O., Heron, T. E., & Heward, W. L. (2020). Applied Behavior Analysis (3rd ed.). Pearson.
- Ch. 6: Constructing and Interpreting Graphic Displays of Behavioral Data (p. 124)
- Ch. 7: Analyzing Behavior Change: Basic Assumptions and Strategies (p. 155)
- Ch. 8: Reversal and Multielement Designs (p. 171)
- Ch. 9: Multiple Baseline and Changing Criterion Designs (p. 193)
- Ch. 10: Planning and Evaluating Applied Behavior Analysis Research (p. 216)