English

Secretary problem and two almost the same consecutive applicants

Probability 2023-07-10 v2 Combinatorics

Abstract

We present a new variant of the secretary problem. Let AA be a totally ordered set of nn \emph{applicants}. Given PAP\subseteq A and xAx\in A, let rr(P,x)={zPzx}\mboxrr(P,x)=\vert\{z\in P \mid z\leq x\}\vert\mbox{ } be the \emph{relative rank of} xx \emph{with regard to} PP, and let rrn(x)=rr(A,x)rr_n(x)=rr(A,x). Let x1,x2,,xnAx_1,x_2,\dots,x_n\in A be a random sequence of distinct applicants. The aim is to select 1<jn1<j\leq n such that rrn(xj1)rrn(xj){1,1}rr_n(x_{j-1})-rr_n(x_j)\in\{-1,1\}. Let α\alpha be a real constant with 0<α<10<\alpha<1. Suppose the following stopping rule τn(α)\tau_n(\alpha): reject first αn\alpha n applicants and then select the first xjx_j such that rr(Pj,xj1)rr(Pj,xj){1,1}rr(P_j,x_{j-1})-rr(P_j,x_j)\in\{-1,1\}, where Pj={xi1ij}P_j=\{x_i\mid 1\leq i\leq j\}. Let pn,τ(α)p_{n,\tau}(\alpha) be the probability that τn(α)\tau_n(\alpha) selects xjx_j such that rrn(xj1)rrn(xj){1,1}rr_n(x_{j-1})-rr_n(x_j)\in\{-1,1\}. We show that limnpn,τ(α)limnpn,τ(12)=12\mbox.\lim_{n\rightarrow\infty}p_{n,\tau}(\alpha)\leq \lim_{n\rightarrow\infty}p_{n,\tau}\left(\frac{1}{2}\right)=\frac{1}{2}\mbox{.}

Keywords

Cite

@article{arxiv.2106.11244,
  title  = {Secretary problem and two almost the same consecutive applicants},
  author = {Josef Rukavicka},
  journal= {arXiv preprint arXiv:2106.11244},
  year   = {2023}
}
R2 v1 2026-06-24T03:26:06.277Z