In the mean field approximation, p(z|n) is approximated by a factorized distribution q(z), in which all hidden variables are independent: Using q(z) instead of p(z|n), computation of the E-step can be written as follows: The parameters of q(z) are determined such that the KL divergence between q(z) and p(z|n) is minimized.
the approximate distribution q(z) is determined by minimizing under the condition that k q i (z i = k) = 1 for all i.