English

Rearrangements of distributions on integers that minimize variance

Combinatorics 2026-01-21 v2 Probability

Abstract

Which permutations of a probability distribution on integers minimize variance? Let XX be a random variable on a set of integers {x1,,xN}\{x_1, \dots, x_N\} such that P(Xi=xi)=pi\mathbb{P}(X_i = x_i) = p_i, i{1,,N}i \in \{1,\dots,N\}. Let (p(1),,p(N))(p^{(1)}, \dots, p^{(N)}) be the sequence (p1,,pN)(p_1, \dots, p_N) ordered non-increasingly. Let X+X^+ be the random variable defined by P(X+=0)=p(1)\mathbb{P}(X^+=0)=p^{(1)}, P(X+=1)=p(2)\mathbb{P}(X^+=1) = p^{(2)}, P(X+=1)=p(3),,P(X+=(1)NN2)=p(N)\mathbb{P}(X^+=-1)=p^{(3)}, \dots, \mathbb{P}(X^+=(-1)^N \lfloor \frac {N} 2 \rfloor)=p^{(N)}. In this short note we generalize and prove the inequality VarX+VarX\mathrm{Var}\, X^+ \le \mathrm{Var}\, X.

Keywords

Cite

@article{arxiv.2510.07899,
  title  = {Rearrangements of distributions on integers that minimize variance},
  author = {Aistis Atminas and Valentas Kurauskas},
  journal= {arXiv preprint arXiv:2510.07899},
  year   = {2026}
}