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Table 4 Summary of observations from the three-treatment case

From: Investigating the relationship between predictability and imbalance in minimisation: a simulation study

  Predictabilityat P= 1.0, % Na Recommended P-value Predictability at this P-value, % Reduction in predictability, % P-value at which imbalance occurs
One variable
Two categories 33.0 100 0.8b 32.0 1.0 0.7
   200 to 300 0.7 b 33.0 0 0.5
   ≥400 0.7 b 33.0 0 -
Two categories - unequal prevalence   100 1.0 33.0 0 1.0
   200 0.8 b 33.0 0 0.7
   300 0.7 b 33.0 0 0.5
   ≥400 0.7 b 33.0 0 -
Three categories   100 1.0 32.0 0 0.9
   200 0.7 b 32.5 <1.0 0.6
   300 0.7 b 33.0 <1.0 0.5
   ≥400 0.7 b 33.0 <1.0 -
Four categories   100 1.0 32.0 0 0.9
   200 0.9 b 32.5 <1.0 0.8
   300 0.7 b 32.7 <1.0 0.6
   ≥400 0.7 b 32.5 <1.0 0.5
Two variables
Both with 2 categories 56.0 100 0.9 54.0 2.0 0.8
   200 0.7 48.0 8.0 0.6
   300 0.7 48.0 8.0 0.5
   ≥400 0.7 48.0 8.0 -
Both with 2 categories - unequal prevalence   100 1.0 56.0 0 1.0
   200 0.9 54.0 2.0 0.8
   300 0.7 49.0 7.0 0.6
   ≥400 0.7 48.0 8.0 0.5
Three variables
All with 2 categories - equal prevalence 67.0 100 1.0 67.0 0 0.9
   200 to 300 0.7 55.0 12.0 0.6
   ≥400 0.7 56.0 11.0 -
All with 2 categories - unequal prevalence   100 1.0 67.0 0 0.9
   200 to 300 0.7 55.0 12.0 0.6
   ≥400 0.7 55.0 12.0 0.5
Four variables
All with 2 categories - equal prevalence 74.0 100 1.0 74.0 0 1.0
   200 0.8 64.0 10.0 0.7
   300 0.7 57.0 17.0 0.6
   ≥400 0.7 58.0 16.0 0.5
  1. aThe categories of N are dependent upon the point at which imbalance is observed (the value of probability of assignment P). bFor one prognostic variable the reduction in predictability is so small as the probability of assignment P is reduced that the recommended P- value is 1.0.