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Topics - castleca

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Hi,
I am trying to compare the person fit statistics between two models with the same data, but a different dimensional structure (a 1D model compared to a 3D model). When I ask for person fit statistics along with the WLE estimates (by specifying show cases !estimates=wle,pfit=yes), ConQuest produces what looks like a MNSQ statistic accompanying the unidimensional estimates, and a t-statistic for the multidimensional estimates. Is this correct? And if so, is there any way to get a common fit statistic, short of performing the complex calculation (Wang & Chen, 2005) myself? I have attached the WLE estimates from each model. Any help is appreciated.

Thanks,
Courtney

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Questions and Answers / Covariance matrix is not positive definite
« on: April 06, 2017, 06:06:22 PM »
Hello,

I am trying to run a between-item multidimensional partial credit model, with 60 items, 3 dimensions, and 369 cases. The model appears to converge, and it gets 98% through computing empirical errors when it crashes and produces this error message: "Covariance matrix is not positive definite. This error is fatal." I have reexamined my command file and data files several times with no luck - I simply cannot figure out what is causing this problem. Can anyone point me in a helpful direction?

Thank you,

Courtney

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