6.31 Multiple hypergeometric distribution: Consider a finite population of size N in which each member is classified as having one of m mutually exclusive and exhaustive attributes, say, $a_1, \dots, a_m$. For each $j = 1, \dots, m$, let $p_j$ denote the proportion of the population that has attribute $a_j$. Suppose that a random sample of size n is taken without replacement.
.2 Joint and Marginal Probability Mass Functions: Multivariate Case
For $j = 1, \dots, m$, let $X_j$ denote the number of members selected that have attribute $a_j$. Show that the joint PMF of the random variables $X_1, \dots, X_m$ is
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