An introduction to observational and experimental design
Learning Outcomes
On watching this video, students should be able to:
- Distinguish between an observational and experimental study.
- Explain the main reason why a randomised experiment can if done well, be used as a test of causality and why from an observational study we can often only describe associations, discussing in particular:
- The concept of random assignment of the exposure or treatment as the mechanism that controls for unwanted sources of variation between exposure groups/levels and allows causal inference
- Why with observation alone there is no random assignment of exposure, so confounding by other factors should always be considered as an explanation for associations found in an observational study.
- Explain what is meant by stratification and how this is used to control for confounding in observational studies.