# LMER number of observations not adding up to the number of rows in dataframe

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!

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