Single-case experimental and N-of-1 designs
Test change repeatedly within a case
Single-case experimental designs use repeated measurements and planned changes in conditions to investigate effects within an individual or other unit. Withdrawal, alternating-treatment and multiple-baseline designs use different forms of experimental control. N-of-1 trials are a related family of repeated within-person treatment comparisons, often randomised and blinded. They differ fundamentally from descriptive single-case reports.
Use for reversible interventions or staged introductions where frequent reliable measurement is feasible and the effect for an individual or small set of units is substantively important.
Strengths
- Directly examines within-person or within-unit change
- Repeated replication across phases can support experimental control
Limitations
- Carryover and time trends complicate comparisons
- Withdrawal may be unethical or effects may be irreversible
Know the boundary
A simple AB before-after series has weaker control than a replicated experiment; N-of-1 results do not automatically generalise to a population.