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Table 4 I_irt item parameters

From: Measuring the ICF components of impairment, activity limitation and participation restriction: an item analysis using classical test theory and item response theory

  IRT item parameters
  Discrim Difficulty: location parameters
I_irt item a b1
(se)
b2
(se)
b3
(se)
b4
(se)
I1. Does remaining standing for 30 minutes increase your pain? 1.38 -4.25
(0.73)
-2.39
(0.29)
-1.22
(0.16)
-0.07
(0.11)
I2. What degree of difficulty do you have bending and rotating your affected joint? 1.46 -3.55
(0.47)
-2.31
(0.25)
-0.68
(0.12)
1.08
(0.14)
I3. How would you describe the pain you usually have from your joint? 2.33 -5.34
(-)
-2.47
(0.35)
-0.81
(0.09)
1.56
(0.13)
I4. How often have you had severe pain from your arthritis? 2.15 -2.82
(0.30)
-1.67
(0.15)
-0.56
(0.09)
1.21
(0.11)
I5. How active has your arthritis been? 2.50 -2.81
(0.31)
-1.94
(0.17)
-0.50
(0.08)
1.25
(0.11)
I6. Have you been troubled by pain from your joint in bed at night? 1.52 -2.65
(0.30)
-1.22
(0.15)
-0.45
(0.11)
0.75
(0.12)
I7. How severe is your stiffness after first wakening in the morning? 1.81 -2.88
(0.31)
-1.54
(0.15)
0.11
(0.09)
2.02
(0.19)
I8. How severe is your stiffness after sitting, lying or resting later in the day? 1.51 -3.62
(0.52)
-1.64
(0.19)
0.54
(0.11)
2.54
(0.27)
I9. How long has your morning stiffness usually lasted from the time you wake up? 1.34 -3.38
(0.43)
-1.05
(0.16)
0.65
(0.12)
1.57
(0.19)
I11. Have you felt that your knee or hip might suddenly 'give way' or let you down? 1.32 -2.62
(0.32)
-0.79
(0.14)
0.97
(0.14)
2.24
(0.25)
I12. How often have you had pain in two or more joints at the same time? 1.09 -2.43
(0.32)
-0.63
(0.15)
0.76
(0.15)
2.52
(0.31)
I13. Have you had any sudden, severe pain – 'shooting', 'stabbing' or 'spasms' – from the affected joint? 1.33 -2.98
(0.38)
-0.83
(0.14)
1.34
(0.17)
2.72
(0.31)
TOTAL      
  1. Key: Items in bold = items with low discrimination parameter (< 1.25), (-) = not calculated