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7 Command file: Specifying variance structures 1081 Traditional randomised complete block (RCB) analysisThe only random term in a traditional RCBanalysis of these data is the (residual) errorterm e ∼ N(0, σ 2 eI 224). The model thereforeinvolves just one R structure and no G structures(u = 0). In ASReml• the error term is implicit in the model andis not formally specified on the model line,• the IID variance structure (R = σ 2 eI 224) isthe default for error.NIN Alliance Trial 1989variety !Aidpidrawrepl 4.row 22column 11nin89.asd !skip 1yield ∼ mu variety replImportant The error term is always present in the model but its variance structuredoes not need to be formally declared when it has the default IID structure.2a Random effects RCB analysisThe random effects RCB model has 2 randomterms to indicate that the total variation inthe data is comprised of 2 components, a randomreplicate effect u r ∼ N(0, γ r σ 2 eI 4) whereγ r = σ 2 r/σ 2 e, and error as in 1. This model involvesboth the original implicit IID R structureand an implicit IID G structure for therandom replicates. In ASReml• IID variance structure is the default for randomterms in the model.NIN Alliance Trial 1989variety !Aidpidrawrepl 4.row 22column 11nin89.asd !skip 1yield ∼ mu variety !r replSee Section 6.4For this reason the only change to the former command file is the insertion of !rbefore repl. Important All random terms (other than error which is implicit)must be written after !r in the model specification line(s).