I have a dataset with some missing values. I used SPSS for multiple imputation to have a dataset with no missing values (for AMOS). How should I save and use the pooled outcome in AMOS?
Patrick, it is a bit irresponsible to suggest that "SPSS does only single imputation", when even a very cursory Google search shows that it does multiple imputation. See the links below, for example. The 3rd link is for a PDF of Chapter 5 from John Graham's book on missing data (see the 4th link). HTH.
No worries, Patrick--and thanks for taking my remarks in such an even-handed manner. It just irks me (as a long-time SPSS user) that many people form impressions about what SPSS can and cannot do on the basis of very little or very weak evidence. I posted a mini rant on this to the SPSSX-L discussion forum back in January--see the link below if you're interested. :-)
p.s. - As a long-time SPSS user, I am certainly aware that in comparison to some of the other major packages, SPSS often does take its sweet time developing procedures for newer methods. E.g., the genearlized linear model procedure (GENLIN) appeared LONG after the corresponding PROC was available in SAS (and probably Stata too). So I'm not arguing SPSS is perfect, just that it's not as limited as some users of other packages often think. ;-)
Thank you for all your comments. Yes I have used SPSS doe multiple imputation of data. However, results are only usable inside SPSS and you cannot export the outcome to any other package because SPSS performs analysis based on 5 imputed versions and then creates a pooled answer for the analysis (not a pooled dataset).
I am also aware that AMOS can handle missing data using Maximum Likelihood Method technique, but the point is some features of AMOS do not work with missing data and are active merely with complete data (such as modification indices). Besides, sometimes missing data could be the source of some problems with model identification (according to AMOS 22 user guide page 272-273). Hence, I decided to complete the data and then use the outcome in AMOS.
I guess I should go with single imputation as I have around 2-5% missing data or use R.
Let's go back to the original question. Reza wrote (with emphasis added):
I used SPSS for multiple imputation to have a dataset with no missing values (for AMOS). How should I save and use the pooled outcome in AMOS?
As far as I can see, we don't know the answers to these important questions:
What type of analysis did you perform with SPSS? (This will determine what the "pooled outcome" you refer to consists of. E.g., if you were estimating some kind of regression model, the outcome will be a table of pooled estimates of the regression coefficients.)
What did you hope to do with the "pooled outcome" in AMOS?
In a later post, Reza wrote this:
However, results are only usable inside SPSS and you cannot export the outcome to any other package because SPSS performs analysis based on 5 imputed versions and then creates a pooled answer for the analysis (not a pooled dataset).
And then Pat wrote:
Ah, if SPSS can only export a single dataset, that was probably the source of my confusion!
I'd like to clarify that regardless of what software one is using, multiple imputation is never about generating one "pooled" data set. It is about generating multiple imputed data sets, performing the desired analysis on each of those data sets, and then generating pooled estimates of the results (e.g., regression coefficients & their associated SEs). So this is not some limitation of SPSS--it would apply equally to any other package.
Second, the 5 (or however many) imputed data sets generated by the MULTIPLE IMPUTATION procedure in SPSS are all in the same data file. There is a variable called Imputation_ that is equal to 0 for the original data set, and to 1 through m for the m imputed data sets. (When you perform the actual analysis, the file is SPLIT BY Imputation_. This is what tells SPSS go generate the pooled estimates.) So if you are trying to use those multiple imputed data sets in AMOS, I don't see what the problem is.
Finally, for the sake of those who do not use SPSS (and those who do, but don't bother to read the documentation), a list of SPSS procedures that support computation of pooled estimates from multiple imputed data sets can be viewed at the first link below--click on Procedures That Support Pooling.
HTH.
p.s. - For questions about how to do things with SPSS (and other related products such as AMOS), I would recommend posting to the SPSSX-L mailing list (second link below) rather than to RG. Actual SPSS users participate in that forum, so you might have better luck getting answers to your questions. ;-)