Information Criteria Bug?

Posted on Tue, 07/14/2015 - 18:47

bwiernik Joined: 01/30/2014

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I'm fitting a pseudo-bifactor model to a covariance matrix. When I run summary(), I get the following fit statistics:

observed statistics: 45 estimated parameters: 22 degrees of freedom: 23 fit value ( -2lnL units ): -3093.63 saturated fit value ( -2lnL units ): -3226.707 number of observations: 1131 chi-square: X2 ( df=23 ) = 133.0765, p = 1.748705e-17 Information Criteria: | df Penalty | Parameters Penalty | Sample-Size Adjusted AIC: 87.07654 177.0765 NA BIC: -28.63319 287.7554 217.8771 CFI: 0.9552982 TLI: 0.930032 (also known as NNFI) RMSEA: 0.06505073 [95% CI (0.05250108, 0.07801077)] Prob(RMSEA <= 0.05): 0.009698167

The AIC/BIC values seem wrong. Hand calculations say that AIC should be -3093.63 + 2*23 = -3047.63. Is there a reason it's ending up with the value of 87.07654?

Edit: Per this thread (http://openmx.psyc.virginia.edu/thread/89), OpenMx computes AIC, etc. using the X^2 value, rather than -2LL. This isn't what is described in in the help file for mxSummary (it shows the formula as using -2LL). Perhaps the documentation could be updated?

Replied on Thu, 07/16/2015 - 11:54

AdminRobK Joined: 01/24/2014

agreed

Agreed--the documentation should be clarified.

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Replied on Tue, 07/21/2015 - 12:07

mhunter Joined: 07/31/2009

Oops

Sorry! This is my fault. I wrote the documentation without verifying our actual behavior. I've updated the documentation now to reflect what we actually do.

https://github.com/OpenMx/OpenMx/commit/c155e04dfb1b1ec6ad6cef00a9f86e7e3eb95abb