Overspecified model

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mdr's picture
mdr
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Joined: 02/12/2014

Hi,

I'm new to both SEM and Onyx as my question probably shows.

An SEM model that I've specified with Onyx has the symbol with an exclamation mark displayed, and the associated message tells me that the model is overspecified.

Onyx FAQs notes, "If you obtain this error, you have most likely included more freely estimated parameters in your model than there are observed statistics. Try to fix freely estimated parameters or remove paths."

However, Onyx's Estimate Summary reads:
Observed Statistics : 65.0
estimated Parameters : 24
Restricted Degrees of Freedom: 41.0
Why do I get the error warning when the number of freely estimated parameters (24) is less than the number of observed statistics (65)?

MDR

neale's picture
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Joined: 07/31/2009
Parameters doing the same thing

That the number of parameters must not be greater than the number of statistics is only a necessary condition. It is not a sufficient condition. If you have two parameters doing the same thing in a model - say two ways of generating a correlation between variables that don't affect anything else (a common example would be causal paths A -> B and B -> A) then the model will not be identified. Establishing exactly which elements are (joint) culprits can be done mathematically, but I don't think Onyx does this yet. You can explore by deleting paths to see when the warning disappears.

mdr's picture
mdr
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Joined: 02/12/2014
Thanks

Thank you Neale. I'll try deleting paths to identify the problem. MDR