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Table 6 PHQ9 – Rating Scale Model Error rates by sample size (collapsing across items)

From: Rasch fit statistics and sample size considerations for polytomous data

  Infit t Infit t Infit MNSQ Infit MNSQ Infit MNSQ Outfit t Outfit t Outfit MNSQ Outfit MNSQ Outfit MNSQ
Sample < -2 > 2 < 0.7 > 1.2 > 1.3 < -2 > 2 < 0.7 > 1.2 > 1.3
25 0 0 0 0 2 0 0 0 0 2
50 0 0 0 1 0 0 0 0 0 1
100 0 1 1 0 1 0 0 1 0 1
200 1 1 0 0 2 1 0 0 0 0
400 1 3 0 0 1 1 1 0 0 0
800 2 3 1 0 1 1 2 2 0 0
1600 2 5 0 0 1 2 2 0 0 0
3200 2 5 0 0 1 4 2 0 0 0