arXiv subjects

Stewart N. Ethier

Publications and source records attributed to Stewart N. Ethier.

9 recordsLinked to original sources

arXiv2025

Testing for dice control at craps

Dice control involves "setting" the dice and then throwing them carefully, in the hope of influencing the outcomes and gaining an advantage at craps. How does one test for this ability? To specify the alternative hypothesis, we need a statistical model of dice control. Two have been suggested in the gambling literature, namely the Smith-Scott model and the Wong-Shackleford model. Both models are parameterized by $θ\in[0,1]$, which measures the shooter's level of control. We propose and compare four test statistics: (a) the sample proportion of 7s; (b) the sample proportion of pass-line wins; (c) the sample mean of hand-length observations; and (d) the likelihood ratio statistic for a hand-length sample. We want to test $H_0:θ= 0$ (no control) versus $H_1:θ> 0$ (some control). We also want to test $H_0:θ\leθ_0$ versus $H_1:θ>θ_0$, where $θ_0$ is the "break-even point." For the tests considered we estimate the power, either by normal approximation or by simulation.

stat.ME↗

arXiv2024

Variance reduction in Texas hold'em and in video poker

In Texas hold'em, after an all-in bet is made and called before the flop, the turn, or the river, the two players sometimes agree to run it $n$ times, meaning that the remaining five, two, or one cards are dealt out not just once but $n$ times successively without replacement, with $1/n$ of the pot attached to each run. In $n$-play video poker, five cards are dealt exactly as in the conventional single-play game. After the player chooses which cards to hold, new cards are drawn to replace the discards, not just once but $n$ times independently, with $1/n$ of the bet attached to each draw. In both scenarios the players are attempting to reduce the variance of the return without changing the mean. We quantify the extent to which the variance is reduced.

math.PR↗

arXiv2023

A game-theoretic analysis of baccara chemin de fer, II

In a previous paper, we considered several models of the parlor game baccara chemin de fer, including Model B2 (a $2\times2^{484}$ matrix game) and Model B3 (a $2^5\times2^{484}$ matrix game), both of which depend on a positive-integer parameter $d$, the number of decks. The key to solving the game under Model B2 was what we called Foster's algorithm, which applies to additive $2\times2^n$ matrix games. Here "additive" means that the payoffs are additive in the $n$ binary choices that comprise a player II pure strategy. In the present paper, we consider analogous models of the casino game baccara chemin de fer that take into account the $100\,α$ percent commission on Banker (player II) wins, where $0\leα\le1/10$. Thus, the game now depends not just on the discrete parameter $d$ but also on a continuous parameter $α$. Moreover, the game is no longer zero sum. To find all Nash equilibria under Model B2, we generalize Foster's algorithm to additive $2\times2^n$ bimatrix games. We find that, with rare exceptions, the Nash equilibrium is unique. We also obtain a Nash equilibrium under Model B3, based on Model B2 results, but here we are unable to prove uniqueness.

cs.GT↗

arXiv2023

Does the first-serving team have a structural advantage in pickleball?

In pickleball doubles with conventional side-out scoring, points are scored only by the serving team. The serve alternates during a game, with each team serving until it has faulted twice, except at the beginning of the game, in which case the first-serving team serves until it has faulted once. A game to $n$ can be modeled by a Markov chain in a state space with $4n^2+10$ states. Typically, $n=11$ or $n=15$. The authors, both pickleball players, were motivated by the question in the title. Surprisingly, the answer to that question depends on the number of points needed to win. In a game to 11, the first-serving team has a very slight disadvantage, whereas, in a game to 15, the first-serving team has a very slight advantage. It should be noted that these advantages and disadvantages are so small that they cannot be detected by simulation and are revealed only by an analytical solution. The practical implication is that a team that is offered the choice of side or serve should probably choose side. We investigate the probability of winning a game to 11, as well as the mean and standard deviation of the duration (or the number of rallies) of a game to 11. We compare these results with the corresponding ones when modified rally scoring is used in a game to 21. We also investigate the title question for a hybrid form of rally scoring that combines modified rally scoring and traditional doubles server rotation.

math.PR↗

arXiv2023

Bertrand's analysis of baccarat

Joseph Bertrand [1822--1900], who is often credited with a model of duopoly that has a unique Nash equilibrium, made another significant contribution to game theory. Specifically, his 1888 analysis of baccarat was the starting point for Borel's investigation of strategic games in the 1920s. In this paper we show, with near certainty, that Bertrand's results on baccarat were borrowed, without attribution, from an 1881 paper of Albert Badoureau [1853--1923]. In addition, we discuss Borel's criticisms of Bertrand's analysis, one of which helps to explain why Badoureau's contribution was overlooked until now.

math.HO↗

arXiv2021

Gambler's Ruin and the ICM

Consider gambler's ruin with three players, 1, 2, and 3, having initial capitals $A$, $B$, and $C$ units. At each round a pair of players is chosen (uniformly at random) and a fair coin flip is made resulting in the transfer of one unit between these two players. Eventually, one of the players is eliminated and play continues with the remaining two. Let $σ\in S_3$ be the elimination order (e.g., $σ=132$ means player 1 is eliminated first and player 3 is eliminated second, leaving player 2 with $A+B+C$ units). We seek approximations (and exact formulas) for the elimination order probabilities $P_{A,B,C}(σ)$. Exact, as well as arbitrarily precise, computation of these probabilities is possible when $N:=A+B+C$ is not too large. Linear interpolation can then give reasonable approximations for large $N$. One frequently used approximation, the independent chip model (ICM), is shown to be inadequate. A regression adjustment is proposed, which seems to give good approximations to the elimination order probabilities.

math.PR↗

arXiv2020

Teaching a university course on the mathematics of gambling

Courses on the mathematics of gambling have been offered by a number of colleges and universities, and for a number of reasons. In the past 15 years, at least seven potential textbooks for such a course have been published. In this article we objectively compare these books for their probability content, their gambling content, and their mathematical level, to see which ones might be most suitable, depending on student interests and abilities. This is not a book review (e.g., none of the books is recommended over others) but rather an essay offering advice about which topics to include in a course on the mathematics of gambling.

math.HO↗

arXiv2019

Snackjack: A toy model of blackjack

Snackjack is a highly simplified version of blackjack that was proposed by Ethier (2010) and given its name by Epstein (2013). The eight-card deck comprises two aces, two deuces, and four treys, with aces having value either 1 or 4, and deuces and treys having values 2 and 3, respectively. The target total is 7 (vs. 21 in blackjack), and ace-trey is a natural. The dealer stands on 6 and 7, including soft totals, and otherwise hits. The player can stand, hit, double, or split, but split pairs receive only one card per paircard (like split aces in blackjack), and there is no insurance. We analyze the game, both single and multiple deck, deriving basic strategy and one-parameter card-counting systems. Unlike in blackjack, these derivations can be done by hand, though it may nevertheless be easier and more reliable to use a computer. More importantly, the simplicity of snackjack allows us to do computations that would be prohibitively time-consuming at blackjack. We can thereby enhance our understanding of blackjack by thoroughly exploring snackjack.

math.PR↗

arXiv2016

Wright-Fisher construction of the two-parameter Poisson-Dirichlet diffusion

The two-parameter Poisson--Dirichlet diffusion, introduced in 2009 by Petrov, extends the infinitely-many-neutral-alleles diffusion model, related to Kingman's one-parameter Poisson--Dirichlet distribution and to certain Fleming--Viot processes. The additional parameter has been shown to regulate the clustering structure of the population, but is yet to be fully understood in the way it governs the reproductive process. Here we shed some light on these dynamics by formulating a $K$-allele Wright--Fisher model for a population of size $N$, involving a uniform mutation pattern and a specific state-dependent migration mechanism. Suitably scaled, this process converges in distribution to a $K$-dimensional diffusion process as $N\to\infty$. Moreover, the descending order statistics of the $K$-dimensional diffusion converge in distribution to the two-parameter Poisson--Dirichlet diffusion as $K\to\infty$. The choice of the migration mechanism depends on a delicate balance between reinforcement and redistributive effects. The proof of convergence to the infinite-dimensional diffusion is nontrivial because the generators do not converge on a core. Our strategy for overcoming this complication is to prove \textit{a priori} that in the limit there is no "loss of mass", i.e., that, for each limit point of the sequence of finite-dimensional diffusions (after a reordering of components by size), allele frequencies sum to one.

math.PR↗