Which design uses just one or a few subjects, collecting baseline data during an initial control condition, applying the treatment, then reinstating the original control condition to verify that changes were caused by the intervention?

Which design uses just one or a few subjects, collecting baseline data during an initial control condition, applying the treatment, then reinstating the original control condition to verify that changes were caused by the intervention?

• A. Small n design
• B. Single participant design
• C. Independent samples design
• D. Repeated measures design

Answer: (A)

This is about a small-n study design, where one or just a few participants are studied across multiple phases with repeated measurements. The pattern you described—collecting baseline data under a control condition, applying the treatment, and then reinstating the original control to see if the changes revert—fits the ABAB reversal approach often used in single-case research. The key idea is using a withdrawal or reversal to demonstrate that the treatment, not some other factor, is driving the observed change. That emphasis on few subjects and repeated phase changes is what defines a small-n design. In contrast, an independent samples design would compare separate groups with no repeated switching of conditions; a repeated measures design involves the same participants across conditions but typically does not include a deliberate return to baseline to confirm causality; and while a single participant design shares the same spirit, the broader term used in this context is small-n design, which captures studies with one or a few subjects and multiple, alternating conditions.

This is about a small-n study design, where one or just a few participants are studied across multiple phases with repeated measurements. The pattern you described—collecting baseline data under a control condition, applying the treatment, and then reinstating the original control to see if the changes revert—fits the ABAB reversal approach often used in single-case research. The key idea is using a withdrawal or reversal to demonstrate that the treatment, not some other factor, is driving the observed change. That emphasis on few subjects and repeated phase changes is what defines a small-n design.

In contrast, an independent samples design would compare separate groups with no repeated switching of conditions; a repeated measures design involves the same participants across conditions but typically does not include a deliberate return to baseline to confirm causality; and while a single participant design shares the same spirit, the broader term used in this context is small-n design, which captures studies with one or a few subjects and multiple, alternating conditions.