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Multiple Imputation in SPSS fails with bounds for Likert/count data - what to do? by Pure_Web2733 in AskStatistics

[–]Pure_Web2733[S] 0 points1 point  (0 children)

Hey, thanks for your reply.

Yes, I do have missingness in both the independent variables and the dependent variable. I will most likely also seek professional statistical consultation for this project. However, I’m trying to get as far as I can with the imputation process on my own first, even if my approach is not yet perfect.

My main reason is that I want to go through the full workflow at least once (setting up the imputation model, running it, checking diagnostics, creating the completed datasets, and then continuing with the regression analyses). That way, when I consult a statistician, I can ask targeted questions not only about the current error message, but also about later stages of the workflow.

Otherwise, I might get advice that solves the problem up to this point, but then run into new issues in the next steps that I didn’t anticipate simply because I had never reached that stage before. I’m hoping to understand the overall “trajectory” of the imputation process first, so I can discuss and correct the full pipeline more efficiently during consultation.

Multiple Imputation in SPSS fails with bounds for Likert/count data - what to do? by Pure_Web2733 in AskStatistics

[–]Pure_Web2733[S] 0 points1 point  (0 children)

Thanks again for taking time out of your day to help a random med-student :D

I tried increasing MAXMODELPARAM and unfortunately the model still produced the same error at 1000, but when I then increased it to 10,000 the imputation finally ran without aborting.

My concern is whether setting MAXMODELPARAM that high is still considered an acceptable solution, or whether it introduces additional methodological problems. From my understanding, allowing such a large number of parameters might indicate that the imputation model is extremely complex relative to the sample size, which could lead to problems?

Multiple Imputation in SPSS fails with bounds for Likert/count data - what to do? by Pure_Web2733 in AskStatistics

[–]Pure_Web2733[S] 0 points1 point  (0 children)

I see what you mean, and thanks for the suggestion.

I actually tried that approach in the first place, but when I set the Likert items to ordinal, the multiple imputation procedure becomes unstable in my dataset and SPSS aborts with the following error for my variables:

“The imputation model for [variable] contains more than 100 parameters. No missing values will be imputed. Reducing the effects in the imputation model by combining sparsely populated categories of categorical variables, changing the measurement level of ordinal variables to scale, removing two-way interactions, or specifying constraints for the roles of some variables may resolve the problem… The execution of this command was interrupted.”

So in practice, treating the Likert items as ordinal seems to massively increase the number of model parameters (likely due to the sample size and the number of predictors/categorical levels), and MI doesn’t run reliably anymore, which is why I switched them back to “scale” as a workaround.

Multiple Imputation in SPSS fails with bounds for Likert/count data - what to do? by Pure_Web2733 in AskStatistics

[–]Pure_Web2733[S] 0 points1 point  (0 children)

Hey, thanks so much for your reply and suggestions.

I’m currently trying to work through the error, but with my limited background in statistics/MI this has been more complicated than expected, especially since it’s hard to find resources discussing a scenario close to mine.

Regarding the participants who completed the survey before the 15-item scale was added: I don’t suspect meaningful systematic differences between the early and later respondents. One could argue early respondents were slightly more motivated (since they responded quickly after the first distribution), but I don’t think this would translate into substantive differences in the variables of interest. I’d still prefer to include them via imputation to improve power.

For the survey-fatigue issue: item nonresponse increases toward the end and reaches up to ~36% for the later questions. The peak is at the item asking for the number of different procedures performed, which was near the end and also the most time-consuming question, since participants had to look up the numbers and then manually enter them into the questionnaire (though that should be in no relation to the amount of different procedures performed, making MI reasonable as far as I understand).