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Table 2 Rasch analysis outcomes of person-item parameters for the Malay QIRC

From: The Quality of Life Impact Refractive Correction (QIRC) questionnaire: validation of the Malay-translated version of the QIRC using Rasch analysis

  Malay QIRC
20-item Pilot
(N = 105)
19-item Final
(N = 304)
Parameters Functional Emotional Functional Emotional
Item
 Total 13 7 12 7
 Removed Item 3
 Number 1–13 14–20 1–12 13–19
Category
 Total 5 5 4 5
 Collapsed Category 3
 Ordered? No Yes Yes Yes
Person reliability 0.80 0.79 0.80 0.81
Person separation index 1.98 1.93 2.01 2.06
Item reliability 0.98 0.93 0.99 0.98
Item separation index 6.62 3.77 10.45 6.45
Average infit, MnSq (z-std)
 Participant ability 1.02 (0.0) 0.98 (−0.3) 0.99 (− 0.1) 0.96 (− 0.2)
 Item difficulty 1.00 (0.0) 1.01 (0.0) 0.99 (− 0.2) 1.02 (0.1)
Average outfit, MnSq (z-std)
 Participant ability 1.01 (0.0) 0.98 (−0.3) 1.00 (0.0) 0.97 (−0.2)
 Item difficulty 1.01 (0.0) 0.98 (−0.1) 1.01 (− 0.1) 0.97 (− 0.4)
  1. QIRC Quality of Life Impact Refractive Correction, N number of participants, MnSq mean square, z-std z-standardised