Table 4 Items Hierarchy and fit statistics (items arranged from most difficult to easiest) after removing misfitting patients (run number 2) and before grouping items into two testlets

7 Do heavy household jobs

− 1.39

0.13

− 1.71

4.46

0.108

✓

19 Recreational: Free arm

− 1.09

0.12

0.37

0.58

0.747

✓

11 Carry heavy object

− 1.03

0.12

− 0.36

0.32

0.853

×

25 Pain during activity

− 1.02

0.14

0.34

1.37

0.503

✓

18 Recreational: Force

− 0.89

0.12

0.01

2.55

0.279

×

12 Change bulb overhead

− 0.69

0.12

− 0.63

2.94

0.230

✓

14 Wash your back

− 0.65

0.12

− 0.60

0.50

0.781

✓

6 Place on a shelf

− 0.29

0.13

− 0.75

1.59

0.452

✓

24 Pain

− 0.27

0.14

− 0.82

2.40

0.301

✓

27 Weakness

− 0.24

0.12

0.75

0.13

0.937

✓

1 Open a jar

− 0.21

0.12

1.92

0.97

0.616

×

5 Open heavy door

− 0.18

0.13

− 0.89

5.95

0.051

✓

13 Wash/blow dry hair

0.00

0.12

− 1.73

5.72

0.057

✓

10 Carry shopping bag

0.02

0.12

− 1.32

3.71

0.156

×

8 Garden/yard work

0.03

0.11

− 1.13

1.19

0.550

×

28 Stiffness

0.13

0.11

0.60

7.12

0.029

×

23 Limitation in work and daily activities

0.22

0.13

− 0.67

2.09

0.351

✓

29 Sleep

0.26

0.12

2.14

29.43

 < 0.001

×

9 Make bed

0.35

0.12

− 1.50

3.21

0.201

✓

16 Use a knife to cut food

0.47

0.12

− 1.75

4.84

0.089

✓

20 Manage transportation needs

0.54

0.12

0.88

1.76

0.415

✓

4 Prepare meal

0.65

0.12

0.22

3.89

0.143

✓

26 Tingling

0.67

0.12

3.53

29.93

 < 0.001

✓

22 Interference with social activities

0.69

0.12

1.38

1.74

0.419

×

30 Confidence

0.72

0.12

4.20

29.04

 < 0.001

×

15 Put on sweater

0.72

0.13

− 0.41

0.70

0.705

✓

3 Turn key

0.79

0.12

1.07

1.28

0.528

×

17 Recreational: little effort

0.84

0.13

− 0.63

2.96

0.228

✓

2 Write

0.88

0.12

− 0.59

0.96

0.620

×