When does an association become a cause?

What will you explore?

Bradford Hill, 1965

Correlation isn't causation — but that sentence is only the beginning of the conversation.

How does it work?

Watch a 90-second cinematic explanation, or explore a story that pauses so you can change its central mechanism. Inspect the source evidence, compare outcomes and resume the narration. This free Lesson Worlds adaptation needs no account or download; younger learners may want help from a parent or teacher.

Inside the cinematic story

1. Together does not tell us why.

   An association has possible explanations.

2. The hidden common cause.

   Rain → umbrellas. Rain → puddles.

3. Change what you intervene on.

   Change a cause, or change its companion.

   Take control: What should change? Rain on · Close umbrellas · Rain off

4. Real evidence is less tidy.

   A diagram states assumptions. Evidence tests them.

5. Reason across the evidence.

   No automatic checklist proves causation.

6. Follow the alternative paths.

   What would separate the explanations?

Discuss the evidence

Before starting, explain what you think this claim means: Correlation isn't causation — but that sentence is only the beginning of the conversation. After exploring, choose one stage above and describe what its model helps you see. Separate what you observed in the adaptation from what the original researchers measured.

Read the original publication for its methods, evidence and limitations. Ask which part of the explanation the interactive model leaves out, and what additional evidence you would need to test the claim yourself.

Rain, umbrellas and puddles form an original teaching model, not an example or dataset from Hill's paper. Interventions describe that assumed model only. Hill's viewpoints are not a mechanical proof checklist.

Original research

The Environment and Disease: Association or Causation?

Austin Bradford Hill · Proceedings of the Royal Society of Medicine 58, 295–300 (1965) · 1965

Educational adaptation by Lesson Worlds. Not affiliated with the author or the Royal Society of Medicine. The original publication may have its own access terms.