Decision Forest: A Nonparametric Approach to Modeling Irrational Choice

Customer behavior is often assumed to follow weak rationality, which implies that adding a product to an assortment will not increase the choice probability of another product in that assortment. However, an increasing amount of research has revealed that customers are not necessarily rational when making decisions. In this paper, we propose a new nonparametric choice model that relaxes this assumption and can model a wider range of customer behavior, such as decoy effects between products. In this model, each customer type is associated with a binary decision tree, which represents a decision process for making a purchase based on checking for the existence of specific products in the assortment. Together with a probability distribution over customer types, we show that the resulting model -- a decision forest -- is able to represent any customer choice model, including models that are inconsistent with weak rationality. We theoretically characterize the depth of the forest needed to fit a data set of historical assortments and prove that with high probability, a forest whose depth scales logarithmically in the number of assortments is sufficient to fit most data sets. We also propose two practical algorithms -- one based on column generation and one based on random sampling -- for estimating such models from data. Using synthetic data and real transaction data exhibiting non-rational behavior, we show that the model outperforms both rational and non-rational benchmark models in out-of-sample predictive ability.Comment: The paper is forthcoming in Management Science (accepted on July 25, 2021

Topologies on Types: Connections

For different purposes, economists may use different topologies on types. We char- acterize the relationship among these various topologies. First, we show that for any general types, convergence in the uniform-weak topology implies convergence in both the strategic topology and the uniform strategic topology. Second, we explicitly con- struct a type which is not the limit of any …finite types under the uniform strategic topology, showing that the uniform strategic topology is strictly fi…ner than the strategic topology. With these results, we can linearly rank various topologies on the universal type space, which gives a clear picture of the relationship between the implication of types for beliefs and their implication for behaviors.the universal type space, the strategic topology; the uniform strategic topology; the uniform-weak topology; interim correlated rationalizable actions

A Unified Approach to Information, Knowledge, and Stability

Within the context of strategic interaction, we provide a unified framework for analyzing information, knowledge, and the "stable" pattern of behavior. We first study the related interactive epistemology and, in particular, show an equivalence theorem between a strictly dominated strategy and a never-best reply in terms of epistemic states. We then explore epistemic foundations behind the fascinating idea of stability due to J. von Neumann and O. Morgenstern. The major features of our approach are: (i)unlike the ad hoc semantic model of knowledge, the state space is constructed by Harsanyi’s types that are explicitly formulated by Epstein and Wang (Econometrica 64, 1996, 1343-1373); (ii)players may have general preferences, including subjective expected utility and non-expected utility; and (iii) players may be boundedly rational and have non-partitional information structuresepistemic games; Harsanyi's types; interactive epistemology; stability; non-expected utility; bounded rationality

Symmetry of superconducting states with two orbitals on a tetragonal lattice: application to LaO1−xFxFeAsLaO_{1-x}F_{x}FeAs

We use group theory to classify the superconducting states of systems with two orbitals on a tetragonal lattice. The orbital part of the superconducting gap function can be either symmetric or anti-symmetric. For the orbital symmetric state, the parity is even for spin singlet and odd for spin triplet; for the orbital anti-symmetric state, the parity is odd for spin singlet and even for spin triplet. The gap basis functions are obtained with the use of the group chain scheme by taking into account the spin-orbit coupling. In the weak pairing limit, the orbital anti-symmetric state is only stable for the degenerate orbitals. Possible application to iron-based superconductivity is discussed.Comment: published versio

Quantum Robot: Structure, Algorithms and Applications

A kind of brand-new robot, quantum robot, is proposed through fusing quantum theory with robot technology. Quantum robot is essentially a complex quantum system and it is generally composed of three fundamental parts: MQCU (multi quantum computing units), quantum controller/actuator, and information acquisition units. Corresponding to the system structure, several learning control algorithms including quantum searching algorithm and quantum reinforcement learning are presented for quantum robot. The theoretic results show that quantum robot can reduce the complexity of O(N^2) in traditional robot to O(N^(3/2)) using quantum searching algorithm, and the simulation results demonstrate that quantum robot is also superior to traditional robot in efficient learning by novel quantum reinforcement learning algorithm. Considering the advantages of quantum robot, its some potential important applications are also analyzed and prospected.Comment: 19 pages, 4 figures, 2 table

Correlation of microwave dielectric properties and normal vibration modes of xBa(Mg1/3Ta2/3)O3-(1-x)Ba(Mg1/3Nb2/3)O3 ceramics : II. Infrared spectroscopy

[[abstract]]The relationship between the microwave dielectric properties and the IR active phonons of xBa(Mg1/3Ta2/3)O3 –(12x)Ba(Mg1/3Nb2/3)O3 ceramics was investigated. The IR modes were assigned, and the origin of dielectric response was determined. Among the 15 prominent IR modes, we found that the normal vibrations of the O layers and that of the Ta/Nb layers are strongly correlated to the measured dispersion parameters, such as the resonant strength ~4pr! and the damping coefficient ~g!. The frequency shifts of the normal modes of the O layers and that of the Ta/Nb layers explain the linear decrease of microwave dielectric constant ~K! as x increases, while the width of these modes correlate with the Q3 f value.[[notice]]補正完畢[[journaltype]]國內[[incitationindex]]SCI[[booktype]]紙

Iterated Strict Dominance in General Games

We offer a definition of iterated elimination of strictly dominated strategies (IESDS) for games with (in)finite players, (non)compact strategy sets, and (dis)continuous payoff functions. IESDS is always a well-defined order independent procedure that can be used to solve Nash equilibrium in dominance-solvable games. We characterize IESDS by means of a "stability" criterion, and offer a sufficient and necessary epistemic condition for IESDS. We show by an example that IESDS may generate spurious Nash equilibria in the class of Reny's better-reply secure games. We provide sufficient/necessary conditions under which IESDS preserves the set of Nash equilibria. Nous donnons une définition de l’élimination itérative des stratégies qui sont strictement donimées (EISSD) pour les jeux avec un nombre fini (ou infini) de joueurs , des ensembles de stratégies compactes (ou non-compactes), et des fonctions de gains continues (ou non-continues). Le processus EISSD est bien défini et indépendant de l’ordre d’élimination. Nous donnons une caractérisation du processus EISSD en utilisant un critère de stabilité et offrons une condition épistémologique. Nous démontrons que le processus EISSD peut produire des équilibres faux dans la classe des jeux de meilleures réponses sécuritaires de Reny. Nous donnons des conditions nécessaires et suffisantes pour que le processus EISSD conserve l’ensemble des équilibre de Nash.game theory, strict dominance, iterated elimination, Nash equilibrium, Reny's better-reply secure games., théorie des jeux, dominance stricte, élimination itérative, équilibre de Nash, jeux de meilleures réponses sécuritaires de Reny

Information Design in Optimal Auctions

We study the information design problem in a single-unit auction setting. The information designer controls independent private signals according to which the buyers infer their binary private values. Assuming that the seller adopts the optimal auction due to Myerson (1981) in response, we characterize both the buyer-optimal information structure, which maximizes the buyers' surplus, and the sellerworst information structure, which minimizes the seller's revenue. We translate both information design problems into finite-dimensional, constrained optimization problems in which one can explicitly solve for the optimal information structures. In contrast to the case with one buyer (Roesler and Szentes, 2017), we show that with two or more buyers, the symmetric buyer-optimal information structure is different from the symmetric seller-worst information structure. The good is always sold under the seller-worst information structure but not under the buyer-optimal information structure. Nevertheless, as the number of buyers goes to infinity, both symmetric information structures converge to no disclosure. We also show that in an ex ante symmetric setting, an asymmetric information structure is never seller-worst but can generate a strictly higher surplus for the buyers than the symmetric buyer-optimal information structure

Implementation with Uncertain Evidence

We study a full implementation problem with hard evidence where the state is common knowledge but agents face uncertainty about the evidence endowments of other agents. We identify a necessary and sufficient condition for implementation in mixed-strategy Bayesian Nash equilibria called No Perfect Deceptions. The implementing mechanism requires only two agents and a finite message space, imposes transfers only off the equilibrium, and invoke no device with "...questionable features..." such as integer or modulo games. Requiring only implementation in pure-strategy equilibria weakens the necessary and sufficient condition to No Pure-Perfect Deceptions. In general type spaces where the state is not common knowledge, a condition called higher-order measurability is necessary and sufficient for rationalizable implementation with arbitrarily small transfers alongside

Predicting College Student’ Use of E-Learning Systems: an Attempt to Extend Technology Acceptance Model

This study makes an attempt to extend technology acceptance model (TAM) and presents a respecified conceptual model to examine the factors associated with college students’ use of asynchronous e-learning systems. A web-based learning platform was employed to assist the learning of an undergraduate-level course, management information systems (MIS), in a well-known institute of technology in the southern part of Taiwan. A cross-sectional survey was conducted. The partial least squares method was applied to validate the reliability and validity of the measurement model and assess the proposed conceptual model in this study. The empirical results indicated that college students showed great readiness and positive intentions towards the use of such e-learning system for the professional courses and suggested potential benefits from its use in the long term. The findings of this study not only can proffer practical implications for on-line professional course learning and teaching in business education, but also may serve as instrumental guidelines for e-learning system to be designed effectively to improve students’ interests and motivations in virtual learning environments