Unlike the (single) repeated effect, it is possible to specify up to 10 random effects. Additional random effects can be added by clicking Add Random. To delete a previously specified random effect, click Delete Random. It is not possible to delete all random effects; however, if no entries are made in the random effect, then it will be ignored.
Model terms entered into the Random Effects model produce columns in the Z matrix, constructed in the same way that columns are produced in the X matrix. It is possible to put more than one model term in the Random Effects Model but each random page will correspond to a single variance type. The variance matrix appropriate for that type is sized according to the number of columns produced in that random effect.
The Random Intercept checkbox puts an intercept column (that is, all ones) into the Z matrix.
The Variance Blocking Variables has the effect of inducing independence among the levels of the Variance Blocking Variables. Mathematically, it expands the Z matrix by taking the Kronecker product of the Variance Blocking Variables with the columns produced by the intercept checkbox and the Random Effects Model terms.
The Group model term is used to model heterogeneity of the variances among the levels of the Group model term, similarly to Repeated Effects.
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