Generality of Findings From Single-Case Designs: It’s Not All About the “N”

Walker et al. (2021) wrote a how-to paper for BCBAs. They explain why one-client studies still count as real science.

The authors give clear words you can use when parents or teachers ask, 'But where’s the big group?'

Generality comes from repeating small studies across places, people, and teams—not from one huge sample.

If many single-case studies show the same pattern, you can trust the result for your own client.

Kazdin (2021) adds that most journals still under-use these designs, so Walker’s talking points are needed.

Soto (2020) takes the same logic into brain-behavior work, proving the rule works outside ABA.

Feinstein et al. (1988) showed the nuts and bolts: program stimulus control early, and generalization follows. Walker turns that old idea into today’s friendly script.

Perry et al. (2024) reviewed 22 Turkish parent-run studies. Most skipped generalization probes, just as Walker warns—without planned checks we can’t claim broad change.

Next time a caregiver doubts your ‘tiny’ evidence, quote the replication rule: many small studies beat one big group. Use Walker’s one-page summary in team meetings or insurance reports to show why single-case science is solid enough to fund and follow.