The Four-Dimensional Symptom Questionnaire (4DSQ) in the general population: scale structure, reliability, measurement invariance and normative data: a cross-sectional survey

Table 6 Differential test functioning (DTF) of the 4DSQ scales

4DSQ scale	Factor	DTFR	95 % CI	p	d _DTF	95 % CI
Distress	Education^a
	- Lower	0.127	0.073; 0.180	0.000	0.019	0.011; 0.027
	- Intermediate	0.044	−0.010; 0.099	0.107	0.007	−0.001; 0.015
	Age^b
	- 16–24 years	0.287	0.105; 0.469	0.002	0.043	0.016; 0.070
	- 25–44 years	0.066	−0.080; 0.212	0.377	0.010	−0.012; 0.031
	- 45–64 years	0.095	−0.043; 0.233	0.175	0.014	−0.006; 0.035
Anxiety	Age^b
	- 16–24 years	0.013	−0.050; 0.075	0.686	0.004	−0.017; 0.026
	- 25–44 years	−0.063	−0.113; −0.013	0.014	−0.022	−0.039; −0.004
	- 45–64 years	−0.048	−0.096; −0.001	0.046	−0.016	−0.033; −0.000
Somatization	Education^a
	- Lower	0.083	0.020; 0.146	0.010	0.016	0.004; 0.029
	-Intermediate	−0.013	−0.077; 0.050	0.680	−0.003	−0.015; 0.010
	Age^b
	- 16–24 years	1.234	0.930; 1.539	0.000	0.245	0.185; 0.305
	- 25–44 years	0.561	0.316; 0.806	0.000	0.111	0.063; 0.160
	- 45–64 years	0.355	0.123; 0.587	0.003	0.070	0.024; 0.116
	Gender^c	−0.114	−0.163; −0.064	0.000	−0.023	−0.032; −0.013

DTFR: effect of differential test functioning (DTF; i.e., the effect of differential item functioning on the mean scale score)
d _DTF: effect size of differential test functioning (DTFR / standard deviation of the scale score)
^areference: higher education
^breference: 65+ years
^creference: female

ISSN: 1477-7525