TABLE 1.

Fit indices for the measurement models (N = 314).

Model	χ 2	df	GFI	CFI	NFI	TLI	RMSEA	Model comparisons	Δχ 2	Δdf
Wave 1
(a): Independence model	1893.12	55	0.37	0.00	0.00	0.00	0.33
(b): Single-factor model	475.56	44	0.75	0.77	0.75	0.71	0.18	(a) vs. (b)	1417.56***	11
(c) Proposed model, no covariances	1079.26	49	0.59	0.44	0.43	0.37	0.23	(a) vs. (c)	813.86***	6
(d) Proposed model, covariances allowed	151.72	28	0.93	0.93	0.92	0.87	0.12	(c) vs. (d)	1079.26***	27
Wave 2
(a) Independence model	2038.16	55	0.22	0.00	0.00	0.00	0.34
(b) Single-factor model	487.17	44	0.75	0.78	0.76	0.72	0.18	(a) vs. (b)	1550.99***	11
(c) Proposed model, no covariances	1106.16	49	0.59	0.47	0.46	0.40	0.26	(a) vs. (c)	932.00***	6
(d) Proposed model, covariances allowed	108.68	28	0.94	0.96	0.95	0.92	0.09	(c) vs. (d)	997.48***	27
Measurement invariance tests: Longitudinal comparisons of model (d)
(e) Unconstrained model (baseline model)	321.33	122	0.92	0.96	0.94	0.93	0.07
(f) Baseline model (e), plus factor loadings of engagement and need satisfaction constrained across time	327.80	128	0.92	0.96	0.94	0.93	0.07	(e) vs. (f)	6.47	6
(g) Model (f), plus error variances of the indicators of engagement and need satisfaction constrained across time#	337.89	134	0.91	0.96	0.94	0.93	0.07	(f) vs. (g)	10.09	6

^#The unstandardized loadings of the observed indicators vigor, dedication and absorption on the latent factor Work engagement were 1.08, 1.36, and 1.01, respectively, and their Time 1/Time 2 standardized loadings were 0.83 and 0.86 (vigor), 0.98 and 0.97 (dedication), and 0.80 and 0.83 (absorption). The unstandardized loadings of the observed indicators competence satisfaction, autonomy satisfaction and relatedness satisfaction on the latent factor Need satisfaction were 0.32, 0.42, and 0.63, respectively. Their Time 1/Time 2 standardized loadings were 0.50 and 0.54 (competence), 0.58 and 0.59 (autonomy) and 0.88 and 0.89 (relational). All loadings were significant at p < 0.001.