Comparison of unweighted and item response theory-based weighted sum scoring for the Nine-Questions Depression-Rating Scale in the Northern Thai Dialect

Table 4 DIF analysis between males and females (N = 1,355)

Depressive Symptoms	9Q Score - GRM		9QSF Combination - NRM
Depressive Symptoms	NUDIF	UDIF	NUDIF	UDIF
1. Depressed mood	0.574	0.464	<0.001^a	<0.001^a
2. Markedly diminished interest or pleasure	0.019^a	0.012^a	<0.001^a	<0.001^a
3. Insomnia or hypersomnia	0.166	0.213	0.137	0.106
4. Fatigue or loss of energy	0.557	0.414	<0.001^a	<0.001^a
5. Weight loss when not dieting or weight gain	0.006^a	0.003^a	0.009^a	0.009^a
6. Feeling of worthlessness or excessive or inappropriate guilt	0.085	0.059	0.333	0.341
7. Diminished ability to think or concentrate, or indecisiveness	0.454	0.388	<0.001^a	<0.001^a
8. Psychomotor agitation or retardation	0.115	0.072	<0.001^a	<0.001^a
9. Recurrent thoughts of death, recurrent suicidal ideation, or a suicide attempt or a specific plan for committing suicide	0.594	0.827	0.006^a	0.001^a

9Q The Nine-Questions Depression-Rating Scale, GRM Graded-response model, NRM Nominal-response model, DIF Differential item functioning, NUDIF Non-uniform differential item functioning, UDIF Uniform differential item functioning
^aSignificance of differential item functioning between males and females (p-value < 0.05)

ISSN: 1471-2288