On the Exceedances of Exchangeable Random Variables

Abstract

Suppose that Xn = (X1,…,Xn) have mean 0, and a single-factor covariance Σ = (σij) with σii = 1 and σij = ρ ≥ 0 for i ≠ j. For a threshold c, let Sn be the number of components of Xn that exceed c. We express the distribution of Sn in terms of a single integral, provide the limiting distribution as $n \rightarrow \infty $ , and show that the limit resembles the Beta family. We then describe the shape of the exceedance distribution when the underlying distributions of the single-factor model have a certain likelihood ratio criterion with respect to its scale parameter, and we show that it obeys a majorization ordering.