Research methods in clinical psychology: An introduction for students and practitioners Chris Barker, Nancy Pistrang, and Robert Elliott CHAPTER 9 Small-N designs

Small-N Designs: Overview Single case experiments Naturalistic case studies

Traditions of small-N research Single case studies in medicine and neuropsychology Operant behaviourism Shapiro Personal Questionnaire Idiographic personality research

Single case experiments (N=1 designs) AB design Reversal (ABAB) design Multiple baseline design Changing criterion design

AB design (Use OH with representation of design)

ABAB design (Use OH with representation of design)

Multiple baseline design (Use OH with representation of design)

Changing criterion design (Use OH with representation of design)

Single case experiments: data analysis and generalisation Data displayed on graph –but can use statistical methods Generalisation: –Multiple single case design –Clinical replication series

Naturalistic case studies Narrative case studies Systematic case studies Time-series designs

Narrative case studies Can be used for: –documenting the existence of a phenomenon –disproving a universal proposition –demonstrating a new intervention –generating causal hypotheses Problems: –reliance on memory –“narrative smoothing” –anecdotal

Systematic case studies: increasing internal validity 1. systematic, quantitative (versus anecdotal) data 2. multiple assessments of change over time 3. multiple cases 4. change in previously chronic or stable problems 5. immediate or marked effects following the intervention (Kazdin, 1981; Hayes et al., 1999)

Time-series designs aim: to evaluate causal processes use correlational methods

Small-N designs: Conclusions Good at: –looking at phenomena in depth –disconfirming theories by providing counter-examples –generating hypotheses/theory Poor at: –establishing typicalities or general laws –but “clinical replication series” can test limits of external validity

Methodological pluralism combine large-N and small-N approaches Examples: –Rogers’ (1967) “silent young man” –Parry et al.’s (1986) “anxious executive”