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as BLUP in the literature (McGilchrist 1993), although this modal predictor is neither linear nor unbiased in general. The orthodox BLUP of the ran- dom effects is the linear unbiased predictor of U given Y which minimizes the mean square distance between the random effects U and their predictor within the class of linear functions of Y.

Explicit expressions for the mean square distances between the compo- nents of the random effects U and their predictors are as follows:

ci=E(U^iUi)2=σ21+σ2s=1ah=1qs(i,j,k)R(τsh)wijμijk,h(s), \begin{align} c_i &= E(\hat{U}_i - U_i)^2 \\ &= \frac{\sigma^2}{1 + \sigma^2 \sum_{s=1}^{a} \sum_{h=1}^{q_s} \sum_{(i,j,k) \in \mathcal{R}(\tau_{sh})} w_{ij} \mu_{ijk,h}^{(s)}}, \tag{12} \end{align}

where (i, j, k) runs over the risk set $\mathcal{R}(\tau_{sh})$ for fixed i. Here,

μijk,h(s)=exp(αsh+βxijk(s))=exp((α,β)xijk,h(s))=exp(γxijk,h(s)), \begin{align*} \mu_{ijk,h}^{(s)} &= \exp (\alpha_{sh} + \beta^{\top} \mathbf{x}_{ijk}^{(s)}) \\ &= \exp ((\alpha^{\top}, \beta^{\top}) \mathbf{x}_{ijk,h}^{(s)}) \\ &= \exp (\gamma^{\top} \mathbf{x}_{ijk,h}^{(s)}), \end{align*}

and, for fixed (i, j),

wij=(1+ω2s=1ah=1qs(i,j,k)R(τsh)μijk,h(s))1, w_{ij} = \left( 1 + \omega^2 \sum_{s=1}^{a} \sum_{h=1}^{q_s} \sum_{(i,j,k) \in \mathcal{R}(\tau_{sh})} \mu_{ijk,h}^{(s)} \right)^{-1},

where (i, j, k) runs over the risk set $\mathcal{R}(\tau_{sh})$. Similarly, we have

cij=E(U^ijUij)2=wij{ω2+ciwij}. \begin{align} c_{ij} &= E(\hat{U}_{ij} - U_{ij})^2 \\ &= w_{ij} \{ \omega^2 + c_i w_{ij} \}. \tag{13} \end{align}

The cluster random effects predictor can be expressed as

U^i=1+σ2s=1ah=1qs(i,j,k)R(τsh)wijYijk,h(s)1+σ2s=1ah=1qs(i,j,k)R(τsh)wijμijk,h(s)=ci(1σ2+s=1ah=1qs(i,j,k)R(τsh)wijYijk,h(s)), \begin{align*} \hat{U}_i &= \frac{1 + \sigma^2 \sum_{s=1}^{a} \sum_{h=1}^{q_s} \sum_{(i,j,k) \in \mathcal{R}(\tau_{sh})} w_{ij} Y_{ijk,h}^{(s)}}{1 + \sigma^2 \sum_{s=1}^{a} \sum_{h=1}^{q_s} \sum_{(i,j,k) \in \mathcal{R}(\tau_{sh})} w_{ij} \mu_{ijk,h}^{(s)}} \\ &= c_i \left( \frac{1}{\sigma^2} + \sum_{s=1}^{a} \sum_{h=1}^{q_s} \sum_{(i,j,k) \in \mathcal{R}(\tau_{sh})} w_{ij} Y_{ijk,h}^{(s)} \right), \end{align*}

where (i, j, k) runs over the risk set $\mathcal{R}(\tau_{sh})$ for any given i. The sub-cluster random effects predictors are

U^ij=wijU^i+ω2wijs=1ah=1qs(i,j,k)R(τsh)Yijk,h(s), \hat{U}_{ij} = w_{ij}\hat{U}_i + \omega^2 w_{ij} \sum_{s=1}^{a} \sum_{h=1}^{q_s} \sum_{(i,j,k) \in \mathcal{R}(\tau_{sh})} Y_{ijk,h}^{(s)},