Hi, New to both R and SEM, so this may be a very simple question. I am trying to run a very simple path analysis using the sem package. There are 2 exogenous (FARSCH, LOCUS10) and 2 endogenous (T_ATTENT, RMTEST) observed variables in the model. The idea is that T_ATTENT mediates the effect of FARSCH and LOCUS10 on RMTEST. The RAM specification I used is
FARSCH -> T_ATTENT, y1x1, NA LOCUS10 -> T_ATTENT, y1x2, NA FARSCH -> RMTEST10, y2x1, NA LOCUS10 -> RMTEST10, y2x2, NA T_ATTENT -> RMTEST10, y2y1, NA FARSCH <-> FARSCH, x1x1, NA LOCUS10 <-> LOCUS10, x2x2, NA T_ATTENT <-> T_ATTENT, y1y1, NA RMTEST10 <-> RMTEST10, y2y2, NA LOCUS10 <-> FARSCH, x2x1, NA This model runs, but using the summary function does not return the usual model fit statistics, only the following: Model Chisquare = 0 Df = 0 Pr(>Chisq) = NA Chisquare (null model) = 8526.8 Df = 6 Goodness-of-fit index = 1 BIC = 0 If I omit the last line from the RAM specification(i.e., delete "LOCUS10 <-> FARSCH, x2x1, NA"), I DO get all the usual statistics: Model Chisquare = 1303.7 Df = 1 Pr(>Chisq) = 0 Chisquare (null model) = 8526.8 Df = 6 Goodness-of-fit index = 0.95864 Adjusted goodness-of-fit index = 0.58639 RMSEA index = 0.30029 90% CI: (NA, NA) Bentler-Bonnett NFI = 0.84711 Tucker-Lewis NNFI = 0.082726 Bentler CFI = 0.84712 BIC = 1294.1 My understanding is the you should always put in the correlation between exogenous predictors, but when I do this I don't get fit statistics. Can anyone help me understand what is happening here? Thank you, Ista ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.