Can I use Likert scale and other ordinal data in SEM?
• 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 double-headed arrows) linking the indicators in time 1 and time 2, and also posits direct effects (straight arrows) connecting the time 1 and time 2 latent variables. With this specification, the model is explored like any other. • Can one use simple variables in lieu of latent variables in SEM models? Yes, though this defeats some of the purpose of using SEM since one cannot easily model error for such variables. While one can simply substitute them for latent variables, this is making the very suspect assumption that they are 100% reliable. It is better to make an estimate of the reliability, based on experience or the literature. However, for a varia
