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Table 3 Item reduction results based on the IRT

From: Item reduction and validation of the Chinese version of diabetes quality-of-life measure (DQOL)

Item No.

Step 1. EFA

Step 2. IRT

Factor 1

Factor 2

Discrimination

Item information functionb

Factor loading< 0.3a

< 1a

< 0.5a

1

0.356

0.421c

2.830

> 2, < 2.5

2

0.313

0.405c

2.848

> 2, < 2.5

3

0.342

0.407c

3.496

> 3, < 3.5

4

0.357

0.368c

1.987

> 1, < 1.5

5

0.361c

0.248

0.778

< 0.2

6

0.506c

0.115

1.097

< 0.4

7

0.274

0.181

Removed

8

0.369c

0.258

0.769

< 0.2

9

0.427c

0.203

1.024

< 0.3

10

0.343c

0.153

0.768

< 0.2

11

0.470c

0.160

1.211

< 0.5

12

0.365c

0.184

0.854

< 0.3

13

0.373c

0.171

0.884

< 0.3

14

0.466c

0.218

1.147

< 0.4

15

0.544c

0.207

1.485

> 0.6, < 0.7

16

0.544c

0.045

1.328

> 0.5, < 0.6

17

0.456c

−0.128

1.237

< 0.5

18

0.368c

0.077

0.801

< 0.2

19

0.494c

0.186

1.178

< 0.5

20

0.592c

0.031

1.567

< 0.5

21

0.394c

0.205

0.850

< 0.3

22

0.491c

−0.063

1.506

> 0.6, < 0.7

23

0.220

−0.023

Removed

24

0.352c

0.068

0.793

< 0.2

25

0.404c

−0.076

0.991

< 0.3

26

0.262

−0.150

Removed

27

0.485c

−0.052

1.429

> 0.6, < 0.7

28

0.519c

−0.041

1.517

> 0.7, < 0.8

29

0.173

−0.059

Removed

30

0.575c

−0.087

1.666

> 0.8, < 0.9

31

0.212

−0.017

Removed

32

0.346c

−0.242

0.998

< 0.3

33

0.345c

0.042

0.762

< 0.2

34

0.271

−0.060

Removed

35

0.214

−0.197

Removed

36

0.383c

−0.351

1.068

< 0.4

37

0.449c

−0.162

1.099

< 0.4

38

0.410

−0.514c

0.321

around 0

39

0.403

−0.441c

0.303

around 0

40

0.330

−0.461c

0.360

around 0

41

0.372

−0.510c

0.289

around 0

42

0.433c

−0.182

1.224

< 0.5

43

0.526c

−0.089

1.357

> 0.5, < 0.6

44

0.450c

−0.180

1.306

> 0.5, < 0.6

45

0.479c

0.021

1.048

< 0.4

46

0.465c

−0.280

1.515

> 0.7, < 0.8

  1. Bold and italic number indicates the item failed the corresponding test
  2. Dashed box indicates the item(s) was removed from the scale
  3. aExclusion criteria;
  4. bHighest point on the item information function curve;
  5. cindicates which factor the item belongs to base on the EFA
  6. IRT Item response theory, EFA Exploratory factor analysis