= Count-mixture structural zero
{title2=$\pi$}
= Structural-zero component
{synonym}
A <structural-zero component> in a count mixture produces a count identically equal to zero. If its mixture weight is $\pi$ and the ordinary component also assigns mass $p_0$ to zero, the observed zero probability is $\pi+(1-\pi)p_0$. Thus an observed zero does not reveal the latent component membership. A shared component for a repeated count profile makes the whole profile zero and induces dependence between its components.
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