Suppose there are $K$ distributions $F_1,..,F_K$ and a random variable $x$ such that $E(x | F_i) = \mu_i$. Suppose also that the distributions appear in proportion $p_1 F_1 + ... + p_n F_K$, so that with probability $p_i$, the distribution faced is $F_i$. Is it then the case that $\frac{1}{n} \sum_{i=1}^n x_i \to \sum_{i=1}^K p_i E(x | F_i)$, i.e. does a `mixing' law of large numbers hold?
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