In an A-B-A-B single-case design, what does phase B represent?

In an A-B-A-B single-case design, what does phase B represent?

• A. No treatment.
• B. Treatment is applied.
• C. Withdrawal of treatment.
• D. A different measurement phase.

Answer: (B)

In ABAB designs, phases alternate between baseline (no treatment) and intervention to see if the treatment changes the target behavior. Phase B is the period when the intervention is applied. This is where you observe how behavior changes with the treatment. If the behavior improves during the treatment and then returns toward baseline when the treatment is withdrawn, and improves again when the treatment is reintroduced, that pattern supports that the treatment is producing the change. The initial and final A phases represent no treatment, while withdrawal of treatment occurs when moving back to one of the A phases.

In ABAB designs, phases alternate between baseline (no treatment) and intervention to see if the treatment changes the target behavior. Phase B is the period when the intervention is applied. This is where you observe how behavior changes with the treatment. If the behavior improves during the treatment and then returns toward baseline when the treatment is withdrawn, and improves again when the treatment is reintroduced, that pattern supports that the treatment is producing the change. The initial and final A phases represent no treatment, while withdrawal of treatment occurs when moving back to one of the A phases.