Original article at: http://www.math.washington.edu/~ejpecp/ECP/viewarticle.php?id=1664

Positive correlation for increasing events with disjoint dependencies does not imply positive correlation for all increasing events

Nicholas Weininger, Rutgers University

Abstract

Abstract. A probability measure mu on the lattice 2^[n] is said to be positively associated if any two increasing functions on the lattice are positively correlated with respect to mu. Pemantle asked whether, in order to establish positive association for a given mu, it might be sufficient to show positive correlation only for pairs of functions which depend on disjoint subsets of the ground set [n]. We answer Pemantle's question in the negative, by exhibiting a measure which gives positive correlation for pairs satisfying Pemantle's condition but not for general pairs of increasing functions.

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Original article at: http://www.math.washington.edu/~ejpecp/ECP/viewarticle.php?id=1664