[R] Amelia: pool data from multiple imputated datasets - for descriptives

Rawson, Kerri rawsonk at psychiatry.wustl.edu
Wed Aug 6 22:58:04 CEST 2014

I used AmeliaView to create 5 imputed datasets.  I want to pool the 5 imputed datasets into one to get pooled descriptive information (means, SD, min/max, etc) that is needed to calculate RCI scores (corrected for measurement error and practice effects).

The formula to calculate RCI is ((X2 - X1) - (M2 - M1))/S.E.D.  where
X1 is observed pre-test score
X2 is observed post-test score
M1 is the group mean pre-test score
M2 is the group mean post-test score, and
S.E.D. is the standard deviation of the mean observed difference score.

My data is currently in long form.  I have an ID variable, pre/post data, week, and imputed dataset number.

ID      var1    var2    var3    var4    week    impdataset#
555     16      10      8.87    6       3       1
555     18      12      9       6       7       1
777     12      10      9       7       3       2
777     15      13      8       6       7       2

I have searched several sites, but none of the threads exactly answer my question.

For instance:
I was able to bind/append them into one dataset using:
> ameliaimpute <- rbind(imp1, imp2, imp3, imp4, imp5)
I see I can use packages like Zelig to conduct regression on bound data, but I don't see a way to get the descriptives on pooled data.

I also tried MICE - but it is just appending the imputed datasets also.
>cogspss->read.spss("cogvaronly0806.sav",use.value.labels=TRUE, to.data.frame=TRUE)
>imp <-mice(cogspss, maxit=5)
>com <- complete(imp, "long", inc=TRUE)
>com <- cbind(com, Imputation_ = as.integer(com$.imp)-1)
>write.csv(com, "impmicedata.csv")

One person mentions "I know that I can use Rubin's rules (implemented through any multiple imputation package in R) to pool means and standard errors..."
This sounds like it would answer my question but I have not been able to find a tool that does this.

RStudio Version 0.98.953
AmeliaView 1.7.2.
R x64 3.0.2
Windows 7 Enterprise 64 bit

Thank you for your time.

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