DIFFERENCES BETWEEN ADOLESCENT AND ADULT MOTHERS ...

where all means, variances, and error variances are different across groups to a final
model where these values are constrained to be the same for each group. This hierarchy
of model testing creates a family of nested models, such that one model is a restricted
version of the previous model and these models can be compared using the difference in
chi-squares and their degrees of freedom. If the chi-square difference is significant, then
the restriction is inappropriate and the groups differ on the particular parameter being
tested (Bollen & Curran, 2006).
Measurement model. Before examining the LGC models, a measurement model
was evaluated for the parenting construct. As mentioned, the parenting construct at 4, 8,
and 18 months had three indicators drawn from the IT-HOME: warmth (WM), support
for learning and literacy (SLL), and lack of hostility (LH). Several fit indices were
utilized to determine the goodness of fit of the measurement model and all subsequent
models: Comparative Fit Index (CFI), Root Mean Square Error of Approximation
(RMSEA), and χ 2 . In testing the measurement model all latent factors (4 month parenting,
8 month parenting, and 18 month parenting) were allowed to covary. Error variances of
indicators were also allowed to correlate with each other over time. The measurement
model provided a good fit for the data: χ 2 (15, N = 553) = 35.9, p > .05, RMSEA = .05,
CFI = .97. Furthermore, all indicators loaded significantly on the latent constructs with
small standard errors. Once the appropriateness of the measurement model was
established, tests were conducted to evaluate for measurement invariance over time and
across groups.
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