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Table 5 Item fit statistics of the GAD-7 using the Rasch Rating Scale Models

From: Assessing anxiety among adolescents in Hong Kong: psychometric properties and validity of the Generalised Anxiety Disorder-7 (GAD-7) in an epidemiological community sample

 

Logit of difficulty

Infita

 

Outfitb

 

ρc

Item

Estimate

S.E.

MnSQ

Zstd

MnSQ

Zstd

1. Feeling nervous, anxious, or on edge

−0.88

0.04

0.83

−6.57

0.84

−5.96

.83***

2. Not being able to stop or control worrying

0.21

0.04

0.82

−6.92

0.76

−8.39

.85***

3. Worrying too much about different things

−0.37

0.04

0.89

−4.10

0.87

−4.69

.85***

4. Trouble relaxing

−0.56

0.04

1.01

0.45

1.00

−0.03

.83***

5. Being so restless that it’s hard to sit still

0.79

0.04

0.94

−2.24

0.87

−3.69

.81***

6. Becoming easily annoyed or irritable

−0.35

0.04

1.22

7.66

1.22

7.23

.78***

7. Feeling afraid as if something awful might happen

1.16

0.04

1.33

9.90

1.26

5.53

.74***

  1. S.E. Standard error, MnSQ Mean square, Zstd Standardised score, ρ Spearman’s correlation coefficient, aInfit mean square value should range from 0.6 to 1.4, closer to 1 indicates better fit; bOutfit mean square value should range from 0.5 to 1.7, closer to 1 indicates better fit. cSpearman’s correlation between item and total score