A life-course and time perspective on the construct validity of psychological distress in women and men. Measurement invariance of the K6 across gender

Table 3 Measurement and structural invariance across gender at cycle 1 Young adults (18-39 years old; n = 5748)

Level of invariance	X² df p value	CFI	TLI	RMSEA	Δχ² df^c p value
Measurement invariance
M1. Configural	66.3 14 < .0001	0.993	0.993	0.036	N/A
M2. Metric (vs. M1)	54.7 15 < .0001	0.995	0.995	0.03	8.7 4 0.0679
M3. Tau equivalence (vs. M2)	1108.1 19 < .0001	0.855	0.893	0.141	972.7 5 < .0001
M4. Scalar - Complete (vs. M2)	84.0 25 < .0001	0.992	0.996	0.029	41.5 13 <.0001
M5. Scalar - Partial ^a (vs. M2)	60.3 21 < .0001	0.995	0.997	0.026	11.3 8 0.1828
M6. Scale factor - Partial^b (vs. M5)	62.1 23 < .0001	0.995	0.997	0.024	15.5 10 0.1142
Structural invariance
M7. Latent variances (vs. M6)	48.1 17 < .0001	0.996	0.997	0.025	3.8 1 0.0522
M8. Latent means (vs. M7)	158.2 16 < .0001	0.981	0.983	0.056	69.7 2 < .0001

^a The constraint of equal item threshold was relaxed for item C (restless or fidgety) and item F (everything is an effort).
^b Complete invariance of the scale factors could not be investigated since items C and F had to be unconstrained in the preceding model (i.e., scalar invariance model). No additional items were freed to reach partial scale factor invariance.
^c The degrees of freedom for the chi-square tests are adjusted for the WLSMV estimator and do not correspond to difference of degrees of freedom between the more constrained and the less constrained model.

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