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D.4: Identify the defining features of single-case experimental designs (e.g., individuals serve as their own controls, repeated measures, prediction, verification, replication).

Free practice questions for this part of the BCBA, with an explanation for every option.

In a single-case experimental design, what does it mean to say that the participant 'serves as his or her own control'?
  1. A. A matched participant who does not receive treatment provides the comparison data
    Incorrect. A separate untreated comparison participant is the logic of a group or matched-control design, not single-case logic.
  2. B. The participant's behavior under the intervention is compared with that same participant's behavior under baseline or other conditions
    Correct. Single-case designs compare repeated measures of one individual's behavior across conditions, so that person's baseline is the standard for judging change.
  3. C. The participant records and graphs his or her own behavior
    Incorrect. Self-recording is a measurement method. It has nothing to do with being one's own experimental control.
  4. D. The participant chooses when the intervention starts and stops
    Incorrect. Control over phase changes stays with the experimenter, based on the data. Participant choice is not what this phrase refers to.
In an A-B-A-B design, a client's hand-mouthing falls during the first B phase. When the intervention is withdrawn in the second A phase, hand-mouthing returns to near the original baseline level. In baseline logic, this second A phase mainly provides:
  1. A. Generalization
    Incorrect. Generalization is about behavior change spreading to untrained conditions. It is not one of the elements of baseline logic.
  2. B. Replication
    Incorrect. Replication comes from reintroducing the intervention (the second B phase) and getting the effect again.
  3. C. Verification
    Correct. Returning to baseline and seeing behavior go back to its earlier level verifies the prediction made from the first baseline, which makes it less likely that something else caused the change.
  4. D. Prediction
    Incorrect. Prediction comes from the first stable baseline, which projects what behavior would have done without intervention.
Why do single-case experimental designs rely on repeated measurement of the target behavior within each condition?
  1. A. To show the level, trend, and variability of behavior over time
    Correct. Repeated measurement within each phase shows the level, trend, and variability of the behavior. That is what lets the analyst predict future responding and see whether a change in conditions changed behavior.
  2. B. To check that the intervention is implemented as written
    Treatment integrity is checked by measuring the implementer's behavior, not by repeatedly measuring the client's target behavior.
  3. C. To allow results to be averaged across many participants
    Averaging across participants is a feature of group designs. Single-case designs focus on each individual's behavior.
  4. D. To permit the use of tests of statistical significance
    Single-case designs are mainly analyzed by visual inspection of graphed data. Repeated measurement is not done to permit significance tests.

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