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Simultaneaous MODEL TEST statements v... |
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Hello there, I have a latent growth curve model and wanted to see if the intercept and slope means differed between two groups, so I used the MODEL TEST command. When I run a test simultaneously looking at the two latent constructs, the Wald Test is significant: MODEL TEST: 0 = i1 - i2; 0 = s1 - s2; However, when I run a MODEL TEST for each comparison separately, neither one is significant. I am not sure how to interpret this. Any advice? Thank you. |
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You can interpret this as follows. The two models with 1 constraint fit the data well, however the more constraint model with 2 constraints no longer fits the data well. You can also use LRT(likelihood ratio test) and BIC for inference. |
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While I understand that interpretation, it does not really help me understand the pattern of differences I have found. Neither intercept nor slope differ between the two groups when tested independently BUT when tested together, there is a group difference identified (both by MODEL TEST and by looking at the chi-square difference test of nested models). Can I say that group 1 and group 2 differ in their model of growth? (The intercept and slope are significant. If the significant difference identified when testing the two latent means together, then group 1 shows a lower baseline value and a shallower growth over time than group 2). |
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Testing both together tests whether the line is equal across groups and this is a stronger hypothesis than testing either intercept or slope. The joint test would be the same as the two separate ones only if the two tests were uncorrelated. |
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