has the outcome either way outcome avoided (or caused) by the intervention no outcome
How to say it
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Where I used this
At Praava Health during COVID, we launched door-to-door testing with 6-hour results for travelers.
Read the case: COVID service innovation: door-to-door & 6-hour traveler testing →Everything is calculated in your browser. Nothing you type is sent or stored.
Why absolute risk matters
"Halves your risk" can mean 50 in 100 down to 25, or 2 in 1,000 down to 1. Both are a 50% relative reduction, and they mean completely different things to a patient or a policymaker. Plain-language guidance in health communication consistently recommends showing absolute risks, using the same denominator ("out of 100"), and adding a picture.
- Use frequencies, not percentages. "2 out of 100" is easier to grasp than "2%".
- Keep the denominator fixed. Do not compare "1 in 50" with "1 in 200".
- Show harms the same way as benefits. Side effects deserve the same absolute framing.
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Questions
What is number needed to treat (NNT)?
How many people need the intervention for one person to benefit. It is 1 divided by the absolute risk reduction. An NNT of 50 means treating 50 people prevents one case.
What is the difference between relative and absolute risk?
Relative risk compares the two groups as a ratio. Absolute risk is the actual difference in how many people are affected. Relative numbers look bigger when the starting risk is small.
Where do the risk numbers come from?
From a trial, a study or surveillance data for the group you are talking to. The calculator does the arithmetic; the evidence has to come from a reliable source.