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Table 2 Simulation studya. Comparison of exact and estimated person-years

From: Estimating the standardized incidence ratio (SIR) with incomplete follow-up data

Parameter Mean Standard deviation Median Interquartile range
Person-years (exact) 13466.0 114.7 13467.1 13390.0 – 13544.2
Person-years (estimated) 13409.2 44.3 13408.5 13381.4 – 13435.6
Person-years (biased, if deaths/migration ignored) 14905.3 31.9 14907.2 14884.9 – 14926.9
Number of events 10.95 3.26 11 9 – 13
Number of deaths or migrants 179.7 179 179 172 - 188
Difference exact – estimated person - years 56.8 116.9 58.5 −21.15 – 134.2
Relative difference exact – estimated (in %) 0.41 0.86 0.43 −0.16 – 0.99
  1. aParameter for the simulation
  2. Number of simulation runs 1000
  3. Number of observations 1000
  4. Follow-up duration 15 years
  5. Incidence rates (variable, see table 1)
  6. Mortality rates (variable, see table 1)
  7. Migration rates (variable, see table 1)