Calculate the population attributable risk and fraction with Levin’s formula, Miettinen’s formula or population risks, and the number of preventable cases.
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About this tool
Population attributable risk and fraction with Levin's and Miettinen's formulas.
How to use Population Attributable Risk Calculator
Choose the formula that matches your data.
Enter exposure prevalence and relative risk, the share of cases exposed, or the two risks.
Add the total cases to estimate how many could be prevented.
Worked example
With 25% of people exposed and a relative risk of 3, the population attributable fraction is 33.3%.
What does a PAF of 33% mean?
A third of all cases in the population would not occur if the exposure were removed, if the relationship is causal.
Levin or Miettinen?
Levin’s formula is simple but biased by confounding. Miettinen’s formula with an adjusted relative risk gives a valid estimate.
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