Sample size and mixed models
I would argue that the larger value (individuals) is always more appropriate than the smaller value (clusters). However, the more important issue is that the "ungrouped" version of the likelihood should be used for these calculations. Using the "grouped data" likelihood omits the within cluster variation and inflates the estimate of predictive power. Regards, Rob Kushler
Ben Zuckerberg wrote:
A very quick (and possibly silly) question for mixed modelers. Certain metrics such as Nagelkerke's R2 and the sample size adjusted AICc require the user to specify the sample size. What is the appropriate sample size to use in a mixed model where you might have hundreds of repeat samples on a smaller sample of sites (in this case, the sites are treated as the random factor)? In my case, the lmer output will produce the following information: Number of obs: 10091, groups: ID, 444. For calculating sample size adjusted statistics, would you use an effective sample size of 444? Thank you.
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