I need to use Predictive Mean Matching (PMM) for multiple imputation in SPSS.
According to SPSS support at the following link
https://www.ibm.com/support/knowledgecenter/SSLVMB_24.0.0/spss/mva/syn_multiple_imputation_impute.html
they say "For PMM the imputed value always matches an observed value (specifically, the observed value that is closest to the value drawn by the imputation model).”
SPSS only uses 1 observed value (k = 1) for imputing a missing value. According to Paul Allison, this is insufficient and the default k = 1 should be overridden to k = 5. However, no instructions on how to do this are provided and Allison says in a Q & A at the end of the paper that he does not know how to change the default. This is the link to Allison's article
https://statisticalhorizons.com/predictive-mean-matching
I wrote to SPSS 2 weeks ago but so far haven't heard back. Has anyone come across instructions on how to change the default from k = 1 to k = 5?
Many thanks.
Hi, Judith Fethney
I am struggling with the same issue in SPSS. So I'd like to know if you have got an answer to this and what was the solution?
Short answer is - can't be done in SPSS. I did hear back from them saying exactly that, and that the issue will be looked at in the future. In the end, for the study I am involved in, one of the other researchers was familiar with STATA and was able to do the multiple imputation.
Good luck!
Hi Markus Trämer,
I have version 27 in my use, but still don't have such an option in the Method tab. I did try the Syntax that you proposed [SCALEMODEL=PMM(5)], but it doesn't work. It gives a warning message: 'Subcommand IMPUTE: SCALEMODEL must specify a single unquoted string.
Execution of this command stops.'. Also PMM5, number without parenthesis, is an invalid command.
Because these doesn't work out and because there are no advice in SPSS v.27 syntaxreference that the k-value could be increased from the default value of 1, I think Judith Fethney is right 'can't be done in SPSS'.
Kind regards,
Taija
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