Meaning of variation to managers, researchers and individual patients: questions, methods and time frames
| Role | Question | Methods | Time frame | Variation |
| Health managers | Are we getting better? | Control charts, holistic change | Real time, months' variation | Creating stable processes, learning from special cause |
| Clinical and health-services researchers | Other things equal, does A cause B? | Randomised controlled trials, regression models; reductionist | Not urgent, years | Eliminate special-cause variation, test for significance, focus on mean values |
| Individual patient (and provider) | How can I get better? | Longitudinal, factorial designs | Days, weeks, lifelong | Help in understanding the many reasons for variation in health |