Noureddine El Karoui

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We study regression M-estimates in the setting where p, the number of covariates, and n, the number of observations, are both large, but p ≤ n. We find an exact stochastic representation for the distribution of β = argmin(β∈ℝ(p)) Σ(i=1)(n) ρ(Y(i) - X(i')β) at fixed p and n under various assumptions on the objective function ρ and our statistical model. A(More)
We consider, in the modern setting of high-dimensional statistics, the classic problem of optimizing the objective function in regression using M-estimates when the error distribution is assumed to be known. We propose an algorithm to compute this optimal objective function that takes into account the dimensionality of the problem. Although optimality is(More)
  • N El Karoui, I Karatzas
  • Proceedings of the National Academy of Sciences…
  • 1993
We combine the formulation of Mandelbaum [Mandelbaum, A. (1986) Probab. Theory Rel. Fields 71, 129-147] with ideas from Whittle [Whittle, P. (1980) J. R. Stat. Soc. B 42, 143-149] to obtain a simple and constructive proof for the optimality of Gittins index processes in the general, nonmarkovian dynamic allocation (or "multi-armed bandit") problem. Our(More)
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