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Table 4 Rasch item fit statistics of three overfitting and redundant items (comparison between GRSM and PCM)

From: The Shoulder Function Index (SFInX): a clinician-observed outcome measure for people with a proximal humeral fracture

GRSM Item label PCM
INFIT OUTFIT   INFIT OUTFIT
MNSQ ZSTD MNSQ ZSTD   MNSQ ZSTD MNSQ ZSTD
0.58 −2.0 0.36 −0.9 hitch up trousers 0.68 −1.6 0.39 −0.8
0.48 −4.0 0.33 −2.1 place object above head 0.48 −3.9 0.33 −2.1
0.39 −1.5 0.05 −1.5 light switch 0.35 −1.6 0.05 −1.5
  1. GRSM, Grouped Rating Scale Model; PCM, Partial-Credit Model; MNSQ, Mean Square; ZSTD, Standardised Z-score; SD, standard deviation.