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| Correlation between intercept and slope |
 
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When there is high (almost perfect) correlation between intercept and slope in growith curve model, the model fails to run or gives improper solution.
When I ran the model with random options and analysis it failed to run with saying "nonpositive defninite estimated correlation matrix".
I guess this is the natural reaction of mplus because intercept or slope factor has negative or 0 residual variance if the correlation between them is close to 1(or -1).
Is there any remedy for this problem? |
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| Assuming that the random slope has a significant variance, you could try centering at another time point. |
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I have a similar question. My slope and intercept are highly correlated (more than .80). So far I have done it so, that the loading of the variable at Time 1 is set to 0). However, when I center so that intercept is the last time point, the correlation is even higher. It would not be such a problem, but I am trying to examine whether individual differences in the slope and intercept predict differences in other variables. So...what would be the solution? Should I try to do growth mixture analysis?
Thank you. |
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| I forgot to add...the problem is that when I include both the intercept and slope in the model, all the paths are nonsignificant. However, the paths from the intercept become significant when I fix the paths from the slope to be zero (and the other way around). |
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| Try centering at the average. If that does not help, please send your input, data, output, and license number to support@statmodel.com. |
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