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Table 2 Item reduction results based on the CTT

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

Item No.

Step 1. Item level tests

Step 2. EFA

Step 3. Internal consistency reliability

Missing rate (%)

Mean score

SD

Factor 1

Factor 2

Item-total corrected correlation coefficientb

Cronbach’s alphab

Missing rate > 5%a

< 1.8 or > 4.2a

< 0.67a

Factor loading < 0.3a

r < 0.3a

Increased after removea (Factor 1: 0.884 Factor 2: 0.822)

1

0.312

2.081

0.711

0.384

0.528c

0.667

0.764

2

0.277

2.132

0.693

0.337

0.519c

0.648

0.772

3

0.243

2.078

0.649

0.357

0.550c

0.695

0.751

4

0.104

2.174

0.725

0.388

0.448c

0.564

0.811

5

0.104

2.653

0.926

0.394c

0.172

0.348

0.882

6

0.069

3.129

0.994

0.518c

0.015

0.492

0.879

7

0.069

2.563

0.811

0.297

0.170

Removed

8

0.035

2.740

1.090

0.398c

0.133

0.367

0.882

9

0.139

2.112

0.679

0.420c

0.262

0.360

0.882

10

14.969

2.449

0.769

Removed

11

0.485

2.161

0.692

0.485c

0.234

0.419

0.880

12

0.035

2.594

0.912

0.406c

0.106

0.361

0.882

13

0.312

2.419

0.900

0.398c

0.171

0.345

0.882

14

0.277

2.290

0.748

0.492c

0.236

0.434

0.880

15

0.035

2.158

0.656

0.566c

0.266

0.498

0.879

16

0.139

2.466

1.201

0.557c

−0.137

0.539

0.878

17

0.069

1.727

0.953

0.431c

− 0.166

0.415

0.881

18

0.035

2.321

1.072

0.381c

−0.068

0.379

0.882

19

0.035

2.556

1.075

0.534c

−0.018

0.520

0.879

20

0.069

2.580

1.223

0.608c

−0.165

0.597

0.877

21

0.035

2.631

1.225

0.423c

0.060

0.396

0.882

22

0.069

1.724

0.892

0.492c

−0.124

0.468

0.880

23

0.035

2.729

1.135

0.230

0.006

Removed

24

0.035

2.960

1.239

0.381c

−0.132

0.381

0.882

25

14.414

1.875

0.968

Removed

26

1.802

1.581

0.961

0.245

−0.173

Removed

27

0.416

1.790

1.012

0.487c

−0.144

0.451

0.880

28

0.104

1.843

1.047

0.514c

−0.152

0.490

0.879

29

0.035

2.445

1.176

0.185

−0.228

Removed

30

0.208

1.882

0.977

0.574c

−0.192

0.526

0.878

31

0.035

2.343

1.079

0.222

−0.187

Removed

32

0.069

1.297

0.594

Removed

33

0.104

2.499

1.260

0.355c

−0.089

0.342

0.883

34

0.035

1.781

0.945

0.234

−0.029

Removed

35

8.073

1.136

0.415

Removed

36

2.495

1.229

0.593

Removed

37

0.728

1.888

1.147

0.429c

−0.166

0.420

0.881

38

3.222

1.262

0.685

0.314c

−0.177

0.294

0.883

39

2.668

1.311

0.762

0.332c

−0.197

0.305

0.883

40

4.089

1.134

0.431

Removed

41

3.915

1.213

0.633

Removed

42

0.312

1.641

1.018

0.424c

−0.263

0.414

0.881

43

0.104

1.998

1.151

0.519c

−0.264

0.508

0.879

44

0.069

1.551

0.908

0.441c

−0.225

0.425

0.881

45

0.104

2.632

1.317

0.502c

−0.182

0.487

0.880

46

0.104

1.353

0.720

0.427c

−0.250

0.414

0.881

  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. bTotal scores were calculated as the corrected mean score of the factor
  5. cindicates which factor the item belongs to based on the EFA
  6. CTT Classical test theory, EFA Exploratory factor analysis, SD Standard deviation, N/A Not applicable