Table 4. Dual Change Score Model: Nested Model Comparison Testing Age Group Differences in Parameter Estimates, and Couplings between Perceived Control, and Health.

Model	χ2	df	Δ χ2/df	CFI	RMSEA
	Zero-order model
Full Coupling Model
Baseline	127.22	47	–	0.99	0.03
Variance invariance	268.32	53	141.10 (6)*	0.97	0.05
Covariance invariance	349.71	59	81.39 (6)*	0.96	0.05
Coupling invariance	369.02	61	19.31 (2)*	0.96	0.05
Mean invariance	1,131.52	67	762.50 (6)*	0.85	0.09

Note. Midlife (aged 25 – 64, n = 2,364); Old Age (aged 65 + years, n = 1,238). Baseline model estimates a model that allows for group differences in all model parameters. Variance invariance, covariance invariance, coupling invariance, and mean invariance models constrain the variances in the intercepts and slopes, the random covariances, coupling parameters (i.e., gammas), and the intercepts and slopes (betas set invariant in mean invariance model) to be equal across groups, respectively. CFI = Comparative Fit Index. RMSEA = Root Mean Square Error of Approximation.

^*p < .05 or below.