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 Matt C posted on Wednesday, March 17, 2010 - 12:21 pm

I have a fairly basic question. I ran some initial EFAs on item-level data that I have in SPSS. Responses to the items are reported on ordered categories. Therefore, I imported the data into Mplus (I'm still running version 3.01) using .dat files to run the analyses using EFA with categorical indicators. There are several unrelated sets of items, so I'm actually running a series of EFAs.

One thing I'm noticing is that the number of observations that Mplus is reporting differs from the number of observations reported in the SPSS analyses for some of the EFAs (not all of them), despite the fact that I'm using listwise in both packages. In some cases, the number of observations reported in Mplus exceeds what I was getting in SPSS (e.g., one analysis had 697 observations used in SPSS, while Mplus reported 722). In other cases, the opposite occurs (e.g., one analysis had 560 observations used in SPSS, while Mplus reported only 43). Again, this is only occurring for certain subsets of items; in many cases, the number of observations matches between both packages.

Aside from something odd that might occur when I'm importing the data, is there anything in how Mplus is handling the data that might lead to differences in the number of observations being used in the analyses? It seems somewhat unlikely, but I just wanted to

Thanks for any ideas.
 Linda K. Muthen posted on Wednesday, March 17, 2010 - 2:48 pm
I can't think of anything. It sounds like you either have blanks in your data and are reading it as free format or you are setting the data reading up incorrectly. SPSS uses blanks for missing in some cases. Blanks are not allowed with free format data.
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