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Table 4 Simulated true relative risks (RR's) for multiple physical symptoms and PTSD for a range of hypothesised true prevalence rates. The calculations are based on Stang's algorithm (using an iterative approach to obtain the true RR's).

From: How many mailouts? Could attempts to increase the response rate in the Iraq war cohort study be counterproductive?

Outcome True prevalence (%) True RR
Multiple symptoms:   13.22% error 6.5% error
Observed prevalence 10.84% 6 3.05 1.48
Observed RR 1.22 8 2.15 1.41
  10 1.83 1.35
  12 1.65 1.31
  14 1.52 1.28
  16 1.44 1.26
PTSD    
Observed prevalence 3.90% 3 N/A 5.5
Observed RR 1.09 4 N/A 1.64
  5 N/A 1.35
  7 N/A 1.18
  9 N/A 1.12
  11 1.90 N/A
  13 1.25 N/A
  15 1.16 N/A
  1. * N/A indicates that the true prevalence for this row is not compatible with the specified error rate
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BMC Medical Research Methodology

ISSN: 1471-2288

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