**What are the Bradford Hill criteria useful for?** The Bradford Hill criteria are useful for establishing epidemiologic evidence of a causal relationship between a presumed cause and an observed effect. > **How many principles are in the list of Bradford Hill criteria?** > There are *nine principles* in the list of Bradford Hill criteria. > > **What is a causal relationship?** [(1)](https://en.wikipedia.org/wiki/Causality) > A causal relationship is one where one process contributes to another process taking place. **What are the nine principles of the Bradford Hill criteria?** The nine principles of the Bradford Hill criteria are: 1. Strength (effect size). 2. Consistency (reproducibility). 3. Specificity. 4. Temporality. 5. Biological gradient (dose-response relationship). 6. Plausibility. 7. Coherence. 8. Experiment. 9. Analogy.