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Table 2 Distributions of the difference between the ratio (respectively number of subjects per group) predicted by the model and the one expected by the Raschpower method Δ R (respectively Δ N ) and according to the threshold (Thres) for Δ N

From: A simple ratio-based approach for power and sample size determination for 2-group comparison using Rasch models

Variables

NPOP = 1996077

 

2.5% / Median / 97.5%

[min-max]

ΔR

−0.049 / 0.002 / 0.043

[−1.236 ; 0.230]

ΔN

−10.623 / 0.438 / 13.499

[−179.576 ; 112.064]

 

n (%)

– Thres < ΔN < + Thres

968364 (98.34%)

ΔN < − Thres

10865 (1.10%)§

ΔN > + Thres

5493 (0.56%)†

  1. Thres : threshold corresponding to 5% of the number of subjects per group derived from the Raschpower method.
  2. §: underestimation of the number of subjects per group produced by the model as compared to the Raschpower method; †: overestimation of the number of subjects per group produced by the model as compared to the Raschpower method.
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BMC Medical Research Methodology

ISSN: 1471-2288

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