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Given the parameters and $Z$, the coordinates are conditionally independent. Write $m_i=x_i^T\beta +{\sigma }^2{Z}_i$, $v={\sigma }_0^2$, and let $y_i$ denote the observed count. Their full conditional distributions have scalar densitiesEach is proper: the binomial distribution likelihood factor is bounded, and the remaining factor is a proper normal distribution density.

One completely specified exact algorithm is rejection sampling from $N(m_i,v)$. DefineFor $0<y_i<n_i$,for $y_i=0$ or $y_i=n_i$, take $M_i=1$, and for $n_i=0$ take $H_i=M_i=1$. Propose $t\sim N(m_i,v)$ and accept with probability $H_i(t)/M_i$, repeating until acceptance. The accepted density is proportional to the proposal times $H_i$, exactly $q_i$. Its acceptance probability is positive, so it terminates almost surely, although it can be inefficient.

An efficient exact alternative is adaptive rejection sampling. The log density hasThus it is a log-concave probability density. Choose one tangent point with positive derivative in the left tail and one with negative derivative in the right tail; these exist because the Gaussian term dominates there. Their tangent upper hull gives an integrable piecewise exponential rejection envelope. Sample that envelope, accept using the target-to-envelope ratio, and add evaluated points to improve it. Concavity guarantees the upper bound, so accepted samples remain exact. Sample each coordinate independently by either method; a finite number of Metropolis steps would not provide the requested exact draws.