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Table 3 Rasch analysis results at each run

From: Structural validity of the Arabic version of the disabilities of the Arm, Shoulder and Hand (DASH) using Rasch measurement model

Run

Analysis

N

Item fit residual

Person fit residual

Item-trait interaction

PSI

Unidimensionality T-tests

Mean

SD

Mean

SD

χ2 (df)

P

% of significant tests

1

Initial analysis

109

0.168

1.824

− 0.152

1.741

179.04 (58)

 < 0.001

0.959

19.27%

2

18 misfitting patients removed

91

0.066

1.486

− 0.009

1.169

153.30 (58)

 < 0.001

0.962

15.38%

3

Items grouped into two testlets

91

− 0.016

1.964

− 0.463

0.901

3.99 (4)

0.407

0.934

3.30%

  1. SD = standard deviation; χ2 = Chi-square; df = degrees of freedom; PSI = Person separation index