Table 1

Meaning of variation to managers, researchers and individual patients: questions, methods and time frames

RoleQuestionMethodsTime frameVariation
Health managersAre we getting better?Control charts, holistic changeReal time, months' variationCreating stable processes, learning from special cause
Clinical and health-services researchersOther things equal, does A cause B?Randomised controlled trials, regression models; reductionistNot urgent, yearsEliminate special-cause variation, test for significance, focus on mean values
Individual patient (and provider)How can I get better?Longitudinal, factorial designsDays, weeks, lifelongHelp in understanding the many reasons for variation in health