Pilot Single-Subject Experimental Design
Also known as: pilot SSED, pilot N-of-1 experiment, pilot single-case experimental design, pilot SCED
A pilot single-subject experimental design (pilot SSED) is a small-scale feasibility trial applied to one or very few individuals, combining the repeated-measurement logic of single-subject experimental design with the explicit preparatory aims of a pilot study. It is used to test an intervention protocol, measurement procedures, and design logistics before committing to a full-scale single-case or group experiment.
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When to use it
Use a pilot SSED when you are developing or adapting an intervention for a specific individual or population and need to test whether your protocol is deliverable and your measures are workable before a full SSED or group trial. It is well suited to applied behavior analysis, rehabilitation, clinical psychology, and special education, where interventions are individualized and early feasibility data can prevent costly failures. Do not use it as a stand-alone study claiming definitive causal conclusions; the sample of one or two participants does not support confident generalization, and inferential statistics are inappropriate. Also avoid it if the primary aim is to determine treatment efficacy — that requires a properly powered full SSED or randomized trial.
Strengths & limitations
- Provides concrete feasibility evidence (fidelity, adherence, measure sensitivity) before resource-intensive full studies.
- Generates preliminary visual effect-size data that can inform sample-size planning for subsequent group designs.
- Requires only one or a very small number of participants, making it practical for rare conditions or specialist settings.
- Reveals protocol problems early — allowing adjustments that improve the quality of the definitive study.
- Aligns with ethical principles by limiting participant exposure to an unproven protocol.
- Results from a single participant cannot be generalized; causal conclusions require replication across individuals and settings.
- Small number of data points per phase may not meet minimum stability or data-point criteria recommended for rigorous SSED (typically at least 5 data points per phase).
- Risk of researcher optimism bias: a promising pilot signal may encourage proceeding even when feasibility criteria are not fully met.
- Formal statistical tests are usually inappropriate; analysis relies on visual inspection and descriptive feasibility metrics.
Frequently asked
How is a pilot SSED different from a regular AB design?
Both collect baseline and treatment-phase data on one individual. The difference lies in purpose and primary outcome: a regular AB design aims to demonstrate a functional relationship between the intervention and the target behavior, whereas a pilot SSED explicitly targets feasibility — fidelity, adherence, measure practicality, and protocol workability. The pilot's conclusions are about whether to proceed and what to change, not whether the intervention caused the change.
Can I use inferential statistics in a pilot SSED?
Formal inferential tests are rarely appropriate. With one or two participants and a small number of data points, statistical assumptions cannot be met and p-values would be misleading. Visual analysis of phase-change graphs and descriptive feasibility metrics (fidelity percentage, session completion rate) are the appropriate analytic tools.
How many data points per phase do I need?
Rigorous SSED guidelines typically recommend at least five data points per phase to assess trend and stability. In a pilot SSED this may be relaxed slightly given resource constraints, but collecting fewer than three points per phase makes even preliminary visual analysis unreliable. Document your rationale for any deviation from standard criteria.
Does a pilot SSED require ethics approval?
Yes. Even though only one participant is involved, the study applies an experimental intervention and collects personal data. Standard ethics review and informed consent procedures apply, and any safety-monitoring plan appropriate for the intervention should be in place.
When should I move to a full study instead of a pilot?
Proceed to a full SSED when pre-specified feasibility criteria are met — for example, fidelity above 80%, session completion above 90%, and stable baseline data achievable within a defined time window. If criteria are not met, revise the protocol rather than treating the pilot data as a full study.
Sources
- Thabane, L., Ma, J., Chu, R., Cheng, J., Ismaila, A., Rios, L. P., ... & Goldsmith, C. H. (2010). A tutorial on pilot studies: the what, why and how. BMC Medical Research Methodology, 10(1), 1. DOI: 10.1186/1471-2288-10-1 ↗
- Kazdin, A. E. (2011). Single-Case Research Designs: Methods for Clinical and Applied Settings (2nd ed.). Oxford University Press. ISBN: 978-0195341881
How to cite this page
ScholarGate. (2026, June 3). Pilot Single-Subject Experimental Design. ScholarGate. https://scholargate.app/en/experimental-design/pilot-single-subject-experimental-design
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
- AB DesignExperimental design↔ compare
- ABA DesignExperimental design↔ compare
- Adaptive Single-Subject Experimental DesignExperimental design↔ compare
- Multiple Baseline DesignExperimental design↔ compare
- Pilot Randomized Controlled TrialExperimental design↔ compare
- Single-Subject Experimental DesignExperimental design↔ compare