Infinite Parameter Estimates in Logistic Regression, with Application to Approximate Conditional Inference

This paper discusses recovery of information regarding logistic regression parameters in cases when maximum likelihood estimates of some parameters are infinite. An algorithm for detecting such cases and characterizing the divergence of the parameter estimates is presented. A method for fitting the remaining parameters is also presented . All of these methods rely only on sufficient statistics rather than less aggregated quantities, as required for inference according to the method of Kolassa & Tanner (1994). These results are applied to approximate conditional inference via saddlepoint methods. Specifically, the double saddlepoint method of Skovgaard (1987) is adapted to the case when the solution to the saddlepoint equations exists as a point at infinity     

The birthday problem

Happy Birthday! If it is not your birthday today, it may well be the birthday of someone in your office, or in your class at school. Possibly, it is the birthday of two people in your office or your class. Just how big does a group have to be before its members are likely to share a birthday? Mario Cortina Borja and John Haigh explain the birthday problem.     

How NASA moved from R & D to operations

This paper investigates the initial planning process for the transition of an organization from a R & D environment to an Operations environment. Using a developed transition life cycle model, the paper demonstrates a four step analysis of the management of the transition. Further, the paper suggests the utilization of existing methods for achieving a smooth transformation under various levels of technical, political, cultural, managerial, and economic uncertainties. Finally, the paper lists possible courses of action and considerations for the transition once the initial planning stage is completed. The concepts herein were used to begin planning the change, from R & D to Operations, of the Space Shuttle Program at NASA.     

Young and Unemployed

Unemployment can pose particular problems for school leavers and other young people. Some English studies on the effects of unemployment are reviewed, and some of the causes and effects of unemployment among young people in Australia are then discussed. Some suggestions are made for areas in which further research could be carried out.     

The quantification of smiling using a microcomputer-based approach

This study examines the relationship between the ratings made of a set of smiling and neutral expressions and the facial features which influence these ratings. Judges were shown forty real face photographs of smile and neutral expressions and forty line drawings derived from these photographs and were asked to rate the degree of smiling behavior of each expression. The line drawings of the face were generated by a microcomputer which utilizes a mathematical model to quantify facial expression. Twelve facial measures were generated by the computer. Significant differences were found between the ratings of smile and neutral expressions. The Mode of Presentation did not contribute significantly to the ratings. Using the facial measures as separate covariates, five mouth measures and one eye measure were found to discriminate significantly between the ratings made on smile and neutral expressions. When entered as simultaneous covariates, only four mouth measures contributed to the differences found in the expression ratings. Future research projects which may utilise the computer model are discussedThe research reported in this paper was conducted in the Department of Psychology, University of Adelaide. The authors would like to thank Ulana Sudomlak for her assistance in the gathering and recording of the data for this project, and the reviewers for their helpful comments on an earlier version of this paper.     

Political–economic equilibrium when parties represent constituents: The unidimensional case

 A political–economic environment is studied in which two parties, representing different constituencies of citizens, compete over a proportional tax rate to be levied on private endowments, to finance a public good. Although parties know the distribution of citizen traits (preferences and endowments), they are uncertain about the distribution of traits among the citizens who will turn up at the polls. This uncertainty engenders an endogenously derived function π(t ₁, t ₂) giving the probability that any one tax policy t ₁ will defeat another t ₂ in the election. Equilibrium existence theorems are proved, and the nature of equilibrium is compared with the equilibrium that exists when Downsian parties (ones whose objective is to maximize the probability of victory) face uncertainty. Both constituency-representing parties and uncertainty are needed to generate equilibria in which parties propose different policies. Received: 4 April 1995/Accepted: 2 April 1996     

Contributors to this issue

Contributors to this issue