In the 'pairs' function when doing pairwise comparisons after emmeans, tukey is set as default for adjustment of p-values. But what type of tukey is used, is it tukey-kramer? How can I know this? If its not, is it possible to change to that? To account for unbalanced data.

  dflm1 <- lmer(formula= df[,i] ~ color + 
             (1|id), data=df) 
  emm <- emmeans(dflm1,"color")
  emm_df <- data.frame(emm)
  e <- pairs(emm, adjust="tukey") 
   # tukey-kramer? Or how to change to that?

1 Answer 1


This means it obtains P values from the pstudent() function in R. For unbalanced data (or in general, for unequal SEs or non-spherical correlation structure), this is only an approximate correction for multiplicity.

In the case of a one-way layout with independent samples, that is indeed the Tukey-Kramer method.

For mixed models, factorial experiments, etc., it depends on what you mean by "Tukey-Kramer." If by that you mean using the formulas that apply to a oneway layout, it isn't doing that because the SEs are obtained from the model, which isn't the standard one-way model. But if you interpret "Tukey-Kramer" to mean using the Tukey adjustment method in a case where it doesn't exactly apply, then it is doing that.


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