[R] Paired sample t-test with mi.t.test

Prof. Dr. Matthias Kohl Matthias.Kohl at stamats.de
Fri Apr 7 21:26:55 CEST 2017

Dear Joel,

are you trying to apply function mi.t.test from my package MKmisc?

Could you please try:
mi.t.test(implist, "pre_test", "post_test", alternative =
"greater", paired = TRUE, var.equal = TRUE, conf.level = 0.95)

x and y are the names of the variables, not the variables themselves.


Am 06.04.2017 um 18:32 schrieb Joel Gagnon:
> Dear all,
> It is my first time posting on this list so forgive me for any rookie
> mistakes I could make.
> I want to conduct t-tests on a dataset that has been imputed using the mice
> package:
> imput_pps <- mice(pps, m=20, maxit=20, meth='pmm') # pps is my dataset. It
> contains items from an 11-item questionnaire gather at pre and post test.
> So the data set has 22 columns.
> I then proceed to compute the total scores for the pre and post test on my
> imputed datasets:
> long_pps <- complete(imput_pps, action ="long", include = TRUE)
> long_pps$pre_test <- rowSums(long_pps[ ,c(3:13)])
> long_pps$post_test <- rowSums(long_pps[ , c(14:24)])
> I then used as.mids to convert back to mids object:
> mids_pps <- as.mids(long_pps)
> Next, I created an imputation list object using mitools:
> implist <- lapply(seq(mids_pps$m), function(im) complete(mids_pps, im))
> implist <- imputationList(implist)
> Now, I want to conduct t-tests using the mi.t.test package. I tried the
> following code:
> mi.t.test(implist, implist$pre_test, implist$post_test, alternative =
> "greater", paired = TRUE, var.equal = TRUE, conf.level = 0.95)
> When I run this code, R tells me that Y is missing. I know this may sound
> stupid, but I thought that I specified Y with this line: implist$pre_test,
> implist$post_test - with implist$pre_test being X and implist$post_test
> being Y - like I usually do for a normal t-test using the t.test function.
> It seems I don't quite understand what the Y variable is supposed to
> represent. Could someone help me figure out what I am doing wrong? You
> help would be very much appreciated.
> Best regards,
> Joel Gagnon, Ph.D(c),
> Department of Psychology,
> Université du Québec à Trois-Rivières
> Québec, Canada
> 	[[alternative HTML version deleted]]
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Prof. Dr. Matthias Kohl

More information about the R-help mailing list