Table 4 I_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