![]() In this example, the variance of males ( = 0.120) is approximately six times larger than the variance for females ( = 0.021). This LMM produces the following output in ASReml-R: ![]() In the above model we have a fixed effect of replicate (), and random effects for the parents and their interaction (, and ). Using ASReml-R, the reference model fitted to this data is: mod0 <- asreml(fixed=length~rep, Our response of interest was epicotyl length, the part of the embryonic seedling stem from which the plant’s shoot system develops. ![]() The progeny was evaluated in a randomized complete block design with 4 replicates and planted in large plots. The example comes from Becker (1984) and corresponds to data from 28 white pine ( Pinus monticola) families formed by crossing 4 male to 7 female parents. In this snippet we will briefly explore an example where we constrain two VCs to be identical. There are many reasons why we might want to do this, such as when we combine data from several sources and we want to have a common parameter, or when we want to simplify a model to evaluate a specific hypothesis relating to these components. ![]() Often, after fitting a complex linear mixed model (LMM), we are interested in constraining some of the variance components (VCs).
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