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What are the degrees of freedom for a mixed model R?
Update by StasK: the FAQ on the degrees of freedom for a comparable mixed model R package lmer points to a post on R-help mailing list by Douglas Bates, the author of the package, explaining the controversies surrounding these degrees of freedom. Thanks for contributing an answer to Cross Validated!
How are degrees of freedom assigned in proc mixed?
PROC MIXED then checks whether a fixed effect changes within any subject. If so, it assigns within-subject degrees of freedom to the effect; otherwise, it assigns the between-subject degrees of freedom to the effect (see Schluchter and Elashoff 1990).
Which is the best random and mixed effect model?
We can model such data with the model Y ij = μ+αi+ϵij, (7.1) (7.1) Y i j = μ + α i + ϵ i j, where αi α i is the effect of the i i th machine. As the machines were drawn randomly from a large population, we assume αi i.i.d. ∼ N (0,σ2 α). α i i.i.d. ∼ N ( 0, σ α 2). We also call αi α i a random effect.
Which is the best function for fitting mixed models?
Nonlinear mixed model fitting In order to account for the clustering of observations, we switch to a Nonlinear Mixed-Effect model (NLME). A good choice is the ‘nlme ()’ function in the ‘nlme’ package (Pinheiro and Bates, 2000), although the syntax may be cumbersome, at times.
What are the parameters of a mixed model?
We are mostly interested in the parameters d and e: the first one describes the yield potential of a genotype, while the second one gives a measure of the speed of growth. There are repeated measures in each plot and, therefore, model parameters may show some variability, depending on the genotype, nitrogen level, block and plot.
How to fitting complex mixed models with nlme?
There are repeated measures in each plot and, therefore, model parameters may show some variability, depending on the genotype, nitrogen level, block and plot. In particular, it may be acceptable to assume that b is pretty constant and independent on the above factors, while d and e may change according to the following equations: