Evaluating latent growth curve models using individual fit statistics

The usefulness of assessing individual fit in latent growth curve models was examined. The study used simulated data based on an unconditional and a conditional latent growth curve model with a linear component and a small quadratic component and a linear model was fit to the data. Then the overall fit of linear and quadratic models to these data was examined. The quadratic models fit the data well but the linear models did not, even though the quadratic component was very small. Then fit was examined at the individual level. Based on individual log likelihood values, a linear model fit most of the individual trajectories well. The article then demonstrates the use of individual fit indexes in empirical data and offers suggestions for assessing individual fit in applied research.