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 7 Longitudinal measurement invariance across gender at cycles 1, 4 and 7 Pooled sample (n = 6336^a)

Level of invariance	X² df p value	CFI	TLI	RMSEA	Δχ² df^e p value
Measurement invariance
L1. Configural	240.3 97 < .0001	0.982	0.993	0.022	N/A
L2. Metric (vs. L1)	263.8 98 < .0001	0.98	0.991	0.023	71.0 21 <.0001
L3. Metric - Partial^b (vs. L1)	224.4 100 < .0001	0.985	0.994	0.02	25.5 19 0.1462
L4. Scalar - Partial^c (vs. L3)	309.9 118 < .0001	0.976	0.992	0.023	145.8 40 <.0001
L5. Scalar - Partial^d (vs. L3)	233.6 110 < .0001	0.985	0.994	0.019	45.2 27 0.0154
L6. Scale factor - Partial^c (vs. L5)	234.1 114 < .0001	0.985	0.995	0.018	48.0 32 0.0342
Structural invariance
L7. Longitudinal stability (vs. L6)	111.6 60 < .0001	0.994	0.996	0.016	5.8 5 0.3299
L8. Latent variance (vs. L7)	97.5 54 < .0001	0.995	0.996	0.016	4.4 4 0.3522
L9. Latent means (vs. L8)	198.3 53 < .0001	0.982	0.986	0.029	114.7 6 <.0001
L10. Latent means - Longitudinal (vs. L8)	105.4 55 < .0001	0.994	0.995	0.017	15.0 6 0.0199

^a Number of respondents with complete data for cycles 1, 4 and 7.
^b The constraint of equal factor loadings was relaxed at cycle 1 for item C (restless or fidgety) and over time in men for items B (nervous), C (restless or fidgety) and F (everything was an effort) and for women for items B and F.
^c Complete invariance of the scale factors could not be investigated since some items had to be unconstrained in the preceding models.
^d The constraint of equal items thresholds was relaxed for items A (so sad nothing could cheer you up), B and D (hopeless) at cycle 4 and for items C (restless or fidgety), D and F at cycle 7. In men, item A was freed whereas, in women, the constraint of equal item thresholds was relaxed for all items except E.
^e 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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