The Proof of Function is in the Reversal Design Pudding

Question: How many consecutive phases are required for a reversal design?

Answer: three.

A reversal design requires at least three consecutive phases: Phase 1 – Initial Baseline (A), Phase 2 – Intervention (B), and Return to Baseline – Phase 3; that’s (A). ABA is the minimum number: ABA – Baseline – Intervention – Baseline, is the minimum number. Keep in mind, with each reversal, you strengthen experimental control. So, ABAB is preferred over ABA as a stronger design, and so on. For reversals to occur, the behavior in the return to baseline must approximate the initial baseline levels, basically the same performance levels. And last but not least, the reversal design is the most powerful within-subject design for demonstrating function. Think of it as proof of function.

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