How should one handle missing data in SEM?
• Can I use Likert scale and other ordinal data in SEM? For reasonably large samples, when the number of Likert categories is 4 or higher and skew and kurtosis are within normal limits, use of maximum likelihood estimation (the default in SEM) is justified. In other cases some researchers use weighted least squares (WLS) based on polychoric correlation. However, WLS requires very large sample sizes (>2,000 in one simulation study) for dependable results. Moreover, even when WLS is theoretically called for, empirical studies suggest WLS typically leads to similar fit statistics as maximum likelihood estimation and to no differences in interpretation. • Can SEM handle longitudinal data? Yes. Discussed by Kline (1998: 259-264) for the case of two-points-in-time longitudinal data, the researcher repeats the structural relationship twice in the same model, with the second set being the indicators and latent variables at time 2. Also, the researcher posits unanalyzed correlations (curved dou
