I am trying to run an lmer model with by-participant and by-item random intercepts. My dataframe has 1920 rows in total. The number of items is 32 and the number of participants is 60 (32 * 60 = 1920). When I run an lmer using the lmerTest package, however, I get the following results.

Number of obs: 1824, groups:  participant_id, 57; stimuli_presented, 32

I have checked the levels of my participant_id and it is 60. Why are my 3 participants disappearing? Does this kind of thing happen at all? The following is my code.

data$stimuli_presented <- as.factor(data$stimuli_presented) # 60 levels
data$participant_id <- as.factor(data$participant_id) # 32 levels

model <- lmer(dv ~ iv1 + iv2 + iv3 + iv4 + iv5 + iv6 + iv7 + (1|participant_id) +(1|stimuli_presented), data=data)

Thanks a lot!

  • $\begingroup$ Are there any rows with missing data? $\endgroup$
    – dipetkov
    Sep 23 at 12:58
  • $\begingroup$ You got it, there were some missing rows indeed. Thanks for your help! $\endgroup$
    – user368469
    Sep 26 at 10:45


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