Table 1

Example of incorrect and correct calculation of population attributable fraction for trichotomous “Exposure”1-150

Exposure level% of populationRRCalculation of population attributable fraction (%)
Incorrect1-151Correct1-152
Low501.0
Moderate301.410.79.5
High201.712.311.1
All10023.020.6
  • 1-150 Adapted from table 4 of reference13 by rounding the reported exposure percentages and RRs.

  • 1-151 (0.4 × 0.3) / (1 + 0.4 × 0.3 ) and (0.7 × 0.2) / (1 + 0.7 × 0.2).

  • 1-152 (0.4 × 0.3) / (1 + 0.4 × 0.3 + 0.7 × 0.2 ) and (0.7 × 0.2) / (1 + 0.4 × 0.3 + 0.7 × 0.2).