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Consistency of syntax between lmer and aov_4 #34
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I do not agree. The However, given that we have no replicates, the random intercept model seems indeed the most appropriate, as I have discussed here: http://singmann.org/mixed-models-for-anova-designs-with-one-observation-per-unit-of-observation-and-cell-of-the-design/ So no, To sum this up, random intercept models are in principle dangerous, but somehow okay for this specific case. |
Many thanks for your quick response, and that article, both of which are really helpful in clarifying the problem. I can see that, from the perspective of experimental data where repetitions are the norm, this problem might seem a bit odd. However this type of data (no replicates for each cell of the design and unit of observation) are actually quite common in applied settings where one might want to avoid traditional RM Anova for other reasons (e.g. because of missing or unbalanced data). The most common case in my experience would be a clinical trial with a single outcome and > 2 measurement occasions. It seems a shame that As a consequence I wonder, if nothing else, whether the afex help pages would benefit from a small clarification? Or, even better an amended error message when someone tries to specify The issue is that, because
The issue here is not the rights and wrongs of intercept-only mixed models, but rather the implied promise that |
Am I wrong to think that these two models should do the same thing (or at least, be a close approximation of one another)?
In practice this
aov_4
call doesn't work because it doesn't properly specify the nesting of multiple observations within Subject. To get (what I think is) the equivalent of the lmer model you need to write:I was hoping to be use aov_4 to help students transition between RM Anova and mixed models, but I'm worried these subtle differences in syntax will make it even more confusing than simply using
aov_ez
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