Single case research results as clinical outcomes

The movement toward evidence-based treatments, interventions, or practices pressures single case research (SCR) to use statistical summaries which have broad credibility. These summaries also need to be easily understood and useful in schools and clinics. To date the effect size families, “proportion of variance” (R², Eta²) and “standardized mean difference” (Cohen's d, Hedges' g) have little popularity in SCR. This paper demonstrates a set of alternative Clinical Outcome indices widely used in the field of medicine: Risk Difference, Relative Risk, Relative Risk Improvement, and Odds Ratio, which compare patients in treatment versus control conditions. Translated to SCR designs, the baseline phase becomes the control condition, the intervention phase becomes the treatment condition, and improvement is defined as non-overlapping data between phases. The positive attributes of Clinical Outcomes are demonstrated: (a) easily interpretable results, (b) close relationship with concept of non-overlapping data, (c) minimal data assumptions, (d) minimal statistical expertise required, (e) multiple contrasts possible for diagnostic understanding, (f) exact confidence intervals for results, and (g) close relationship to Pearson R effect size family.