Single subject research is characterized by:

• A. Pre and post test or single case study
• B. Large randomized trials
• C. Cross-sectional surveys
• D. Meta-analyses

Answer: (A)

Single-subject research focuses on the intensive study of an individual (or a very small number of individuals) using repeated measurements over time to determine if an intervention causes a change in a target behavior. The hallmark is collecting data across phases for each subject—typically a baseline period followed by an intervention period (and sometimes multiple baselines or AB designs)—so you can see how the person responds to the treatment rather than averaging results across many people.

The option described fits this approach because it emphasizes pre- and post-testing or a single-case, within-subject design. In practice, you’d track the person’s behavior across time, establish a stable baseline, apply the intervention, and look for changes in level, trend, and variability that align with the treatment, thereby demonstrating a functional relationship for that individual.

The other methods involve different research scales and questions: large randomized trials test effects across groups with random assignment; cross-sectional surveys provide a single snapshot of a population at one time; meta-analyses synthesize results from multiple studies.