Scaling factors, MLR and Decimals PreviousNext
Mplus Discussion > Structural Equation Modeling >
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 Jeremy Miles posted on Friday, May 23, 2008 - 12:24 pm
Hello,
I'm having problems with decimals on the MLR scaling correction factor.
I've got two models which are nested, and the output from Mplus gives:
1: Chi-sq = 1794.786, df= 1246, scf = 1.118
2: Chi-sq = 1802.923, df = 1247, scf = 1.117
When I calculate the difference between the chi-squares, using the formula which incorporates the scaling correction factors, I get, chi-square = -56 (yes, negative).
However, this appears to be due to rounding error. If I change the scaling factor on the second model to 1.1174, I get a chi-square difference of 22 (positive), a massive change.
For some of the models where I'm running this, I can calculate the scaling correction factor 'by hand', by running the ML models and dividing the chi-squares. In which case I find that they are actually 1.117423 and 1.11754, and when I plug those two numbers in, I get a chi-square of 9.
However, I'm running these models with and without weights, and when I run with weights, I can't calculate by hand, I have to use MLR.
So, two questions:
1) Is there a way to make Mplus give more decimal places.
2) One solution that I've tried is to use the average of the two scaling correction factors for both - this works (and in the case that I gave, the average - 1.1175 is very close to both). However, is this going to give me the wrong results on occasion?
Thanks,
Jeremy
 Jeremy Miles posted on Friday, May 23, 2008 - 5:26 pm
I have found a partial solution, which is to use the

savedata:

results are results.dat

And then pulling the scaling correction factor from there. It's not especially easy (as it's not labelled), and it's not ideal, as I don't know when I need the extra precision, and when I don't need this extra precision. (Well, I kind of know that when my chi-square is high, I need lots of precision).

Jeremy
 Linda K. Muthen posted on Saturday, May 24, 2008 - 9:26 am
Yes, results are saved with more decimals. We will add more decimals to the scaling correction factor in the output in the next update.
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