Gennclus: New models for general nonhierarchical clustering analysis

A general class of nonhierarchical clustering models and associated algorithms for fitting them are presented. These (metric) clustering models generalize the Shepard-Arabie Additive Clusters model in allowing for: (1). either overlapping or nonoverlapping clusters; (2). either symmetric (one-way clustering) or nonsymmetric (two-way clustering) proximities (input data); and, (3). either symmetric or diagonal weights. The GENNCLUS algorithms utilize alternating least-squares methods combining ordinary and constrained least-squares, nonlinear constrained mathematical programming, and combinatorial optimization techniques in estimating model parameters. In addition to developing the mathematical bases of these models, a comprehensive set of Monte Carlo simulations of the different models is reported. Two applications concerning brand-switching data and celebrity-brand proximities are discussed. Finally, extensions to three-way models, nonmetric analyses, and other model specifications are provided.Wayne S. DeSarbo is a Member of Technical Staff in the Mathematics and Statistics Research Center at Bell Laboratories in Murray Hill, N.J. I wish to thank R. Gnanadesikan, J. D. Carroll, and P. Arabie for their comments on a previous draft of this paper. I also wish to acknowledge the computer assistance provided by Linda Clark. Finally, I wish to thank the reviewers and editor for their very complete reviews and comments.     

Ordered binary trees constructed through an application of Kendall's tau

A procedure is described for orienting the nodes of a binary tree to maximize the Kendall rank order correlation (tau) between node order and a given external criterion. The procedure is computationally efficient and is based on application of an ordered set of node tests.     

高级职业经理人胜任特质评定探索

为了方便企业甄选所需要的高级管理人才,本文就“高级职业经理人胜任特质评定量表”的编制过程及其量表的结构分析做一报告。该量表分为认知基质、组织协调、领导力、个性倾向和自我调节五个纬度和一个测谎的分量表。本研究立足于中国本土文化,采用小组中心访谈和多种统计分析技术对中国的高级职业经理人的胜任特质进行测评,结果显示总量表和各纬度上的项目具有较高的同质性信度和结构效度,具有较好的鉴别力。     

Comparative evaluation of two superior stopping rules for hierarchical cluster analysis

A split-sample replication stopping rule for hierarchical cluster analysis is compared with the internal criterion previously found superior by Milligan and Cooper (1985) in their comparison of 30 different procedures. The number and extent of overlap of the latent population distributions was systematically varied in the present evaluation of stopping-rule validity. Equal and unequal population base rates were also considered. Both stopping rules correctly identified the actual number of populations when there was essentially no overlap and clusters occupied visually distinct regions of the measurement space. The replication criterion, which is evaluated by clustering of cluster means from preliminary analyses that are accomplished on random partitions of an original data set, was superior as the degree of overlap in population distributions increased. Neither method performed adequately when overlap obliterated visually discernible density nodes.This research was supported in part by NIMH grant 5R01 MH 32457 14.     

Is the “hot‐hands” phenomenon a misperception of random events?

T. Gilovich, R. Vallone, and A. Tversky (1985) asked whether the so-called hot-hands phenomenon – a temporary elevation of the probability of successful shots – actually exists in basketball. They concluded that hot-hands are misperceived random events. This paper re-examines the truth of their conclusion. The present study's main concern was the sensitivity of the statistical tests used in Gilovich et al.'s research. Simulated records of shots over a season were used. These represented many different situations and players, but they always contained at least one hot-hand period. The issue was whether Gilovich et al.'s tests were sensitive enough to detect the hot-hands embedded in the records. The study found that this sensitivity depends on the frequency of hot-hand periods, the total number of shots in all hot-hand periods, the number of shots in each hot-hand period, and the size of the increase in the probability of successful shots in hot-hand periods. However, when the values of those variables were set realistically, on average the tests could detect only about 12% of the hot-hands phenomena.     

Vivid memories of distant trauma: Examining the characteristics of trauma memories and the relationship with the centrality of event and posttraumatic stress 26 years after trauma

In the present study, we investigated the phenomenological characteristics of distant trauma memories and the relationship between the vividness of trauma memories, the centrality of event and symptoms of posttraumatic stress in two groups with different types of trauma exposure, namely survivors and bereaved, from the fire on the passenger ferry, Scandinavian Star, 26 years earlier. More than two decades after the fire, the traumatic event was represented as a vivid, emotional recollection for many of the victims. For both the survivors and the bereaved, a higher degree of vividness of trauma memories and centrality of the event were associated with higher levels of posttraumatic stress. The present findings show that even very distant trauma memories can be represented as vivid recollections. Furthermore, the findings suggest that both vividness of trauma memories and event centrality may contribute to explain how posttraumatic stress reactions can remain present over a very long time.