I'm writing a CFA paper, and I have run into some trouble interpreting the AIC and BIC. This is my first paper using continuous variables, thus the first time I will be reporting these fit statistics and I'm still learning the SEM method overall so bear with me, please.

The paper in question looks at an existing psychometric, but I am scoring it in a slightly different way than was intended. The measure has a frequency of experience and a distress element in it, and usually the frequency of experience is analysed for best fitting model with the distress element later correlated with the model. I have summed both of these elements (frequency scores + distress scores) to produce a new single set of scores which I have then run within a CFA framework (5 factor model using MLR).

The other fit indices look great, however, the AIC and BIC look like this:

CFA on the different elements of the measure:

Frequency : AIC= 12313.226 BiC: 12602.260
Distress  : AIC= 10318.698 BIC: 10607.731
Summed    : AIC= 22039.130 BIC: 22328.163

How would I go about interpreting these values?

  • 1
    $\begingroup$ Can you please clarify exactly what your question is? You seem to be indicating there is something wrong with your AIC/BIC values but I'm not sure what you're referring to. $\endgroup$
    – Macro
    Apr 20 '12 at 14:43
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    $\begingroup$ Are you referring to the magnitude of the absolute values? ICs should not be interpreted on an absolute scale. All seems to be in order $\endgroup$
    – Momo
    Apr 20 '12 at 14:58
  • $\begingroup$ I was talking with a collegue today and showed him the results, he mentioned that the lowest AIC and BIC was a preferable model and by summing the Freq+Distress elements of the measure may have done something as the AIC and BIC looks quite large. To clarify it is the Summed scores I wish to use the AIC and BIC fit statistics look very large when compared to the freq and distress. $\endgroup$
    – Rave
    Apr 20 '12 at 15:10
  • $\begingroup$ As Momo said, the magnitude of an AIC/BIC value should not be interpreted on its own - only AIC/BIC values relative to each other. $\endgroup$
    – Macro
    Apr 20 '12 at 17:05
  • 2
    $\begingroup$ I'm not sure I follow all of this but the summed and non-summed AICs are on different scales (since the likelihood scales with the sample size, which is different in the summed and non-summed groups), so you can't compare them directly. You can only compare them when the data set remains fixed (so the likelihoods are on the same scale). $\endgroup$
    – Macro
    Apr 20 '12 at 22:51

You can check out this book: "Model Selection and Multimodel Inference A Practical Information-Theoretic Approach", Burnham & Anderson 2nd. Ed.

  • $\begingroup$ Welcome to the site, @user13138. Can you say more about this book & why it will address the OP's question? $\endgroup$ Aug 16 '12 at 3:10
  • 3
    $\begingroup$ As Macro said, Section 2.11.1 explains that when the data sets are different, you cannot compare the AIC's. I think that is the reason why the criteria for the summed model are significantly different. Gung, don’t you think the one who asked the question should do a little bit of research him/herself? $\endgroup$
    – Stat
    Aug 16 '12 at 3:45

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