I was wondering whether a growth model with only a linear slope is nested in a model including a linear and quadratic slope. I.e., could these two models be compared using the chi-square test? Or should I use AIC and BIC for model comparison?
With my GMM (default settings with regard to growth factor variances), I received a warning message with the 4-class model related to a not positive definite PSI. I followed your advice, posted in another thread, of constricting the variance of the slope @0 because my slope variance was not significant for the 4-class model. After that, the error message indeed disappeared.
However, for the 1-class and 2-class default GMM models, I did have significant slope variances (for the 3-class model I did not).
With regard to reporting the results in my paper, I wonder whether I should report: (1) 1-class, 2-class and 3-class results for the models with default settings regarding growth factor variance; and 4-class results for the model with s@0 (because I first received the error message for the 4-class model)
(2) reports results for ALL models with s@0, so starting from the 1-class model.
(sidenote: BIC is very comparable for default models and models with s@0, for all classes)
I feel like this question might be related to models being nested; I believe these models are not nested and as such I should start with the 1-class model with s@0 and report those results (so my guess is that I should use option (2)). Am I right?
Thank you for your reply. I am still wondering if, when I go with (1), it would not be wrong to report e.g. the LMR-LRT and BLRT values for a 3-class versus 2-class model, as I worked with s@0 for the 3-class model whereas I did not constrict the slope factor variance for the 2-class model.
Because when I ask for the output of TECH11 and TECH14 for the 3-class s@0 model, it compares this model with a 2-class s@0 model, right? How should I deal with this, as I used a 2-class model without the constricted slope factor variance?