The L2 Rate of Convergence for Event History Regression with Time-dependent Covariates

Consider repeated events of multiple kinds that occur according to a right-continuous semi-Markov process whose transition rates are influenced by one or more time-dependent covariates. The logarithms of the intensities of the transitions from one state to another are modelled as members of a linear function space, which may be finite- or infinite-dimensional. Maximum likelihood estimates are used, where the maximizations are taken over suitably chosen finite-dimensional approximating spaces. It is shown that the L ₂ rates of convergence of the maximum likelihood estimates are determined by the approximation power and dimension of the approximating spaces. The theory is applied to a functional ANOVA model, where the logarithms of the intensities are approximated by functions having the form of a specified sum of a constant term, main effects (functions of one variable), and interaction terms (functions of two or more variables). It is shown that the curse of dimensionality can be ameliorated if only main effects and low-order interactions are considered in functional ANOVA models.     

A generalized step-up-down multiple test procedure

A generalization of step-up and step-down multiple test procedures is proposed. This step-up-down procedure is useful when the objective is to reject a specified minimum number, q, out of a family of k hypotheses. If this basic objective is met at the first step, then it proceeds in a step-down manner to see if more than q hypotheses can be rejected. Otherwise it proceeds in a step-up manner to see if some number less than q hypotheses can be rejected. The usual step-down procedure is the special case where q = 1, and the usual step-up procedure is the special case where q = k. Analytical and numerical comparisons between the powers of the step-up-down procedures with different choices of q are made to see how these powers depend on the actual number of false hypotheses. Examples of application include comparing the efficacy of a treatment to a control for multiple endpoints and testing the sensitivity of a clinical trial for comparing the efficacy of a new treatment with a set of standard treatments.     

Adult-equivalence scales and the economic implementation of interpersonal comparisons of well-being

Equivalence Scale Exactness (ESE) or Independence of Base (IB), a condition on household preferences and interpersonal comparisons, makes adult-equivalence scales independent of utility levels. ESE is characterized by Income-Ratio Comparability (IRC) which assumes that utility equality is preserved by income scaling. If ESE/IRC is a maintained hypothesis, equivalence scales can be estimated from behaviour alone if preferences are not piglog. This condition is not met by a family of translog expenditure functions or by the Almost Ideal Demand System. A translog expenditure function can be used for the reference household, however, together with an independent specification of the equivalence scale.Earlier versions of this paper [1987–1992] have been presented at Amsterdam, Augsburg, Barcelona, Bilbao, CORE, Essex, GREQE, Kiel, Leyden, Madrid, Southhampton, Toulouse, UBC, and Valencia. We thank the seminar participants and the referees of this journal, and are especially indebted to Kenneth Arrow, Martin Browning, Dale Jorgenson, Joseph Ostroy, Shelley Phipps, J. Ruiz-Castillo, Daniel Slesnick, Terry Wales and John Weymark. We also thank Amartya Sen whose remarks on another paper inspired the approach we have taken in this one.     

AUDIO AND VIDEO COMPUTER-ASSISTED SELF INTERVIEWING: Preliminary Tests of New Technologies for Data Collection

Results are reported from a preliminary study testing a new technology for survey data collection: audio computer-assisted self interviewing. This technology has the theoretical potential of providing privacy (or anonymity) of response equivalent to that of paper self-administered questionnaires (SAQs). In addition, it could offer the advantages common to all computer-assisted methods such as the ability to implement complex questionnaire logic, consistency checking, etc.. In contrast to Video-CASI, Audio-CASI proffers these potential advantages without limiting data collection to the literate segment of the population. In this preliminary study, results obtained using RTI's Audio-CASI system were compared to those for paper SAQs and for Video-CASI. Survey questionnaires asking about drug use, sexual behavior, income, and demographic characteristics were administered to a small sample (N = 40) of subjects of average and below-average reading abilities using each method of data collection. While the small sample size renders many results suggestive rather than definitive, the study did demonstrate that both Audio- and Video-CASI systems work well even with subjects who do not have extensive familiarity with computers. Indeed, respondents preferred the Audio- and Video-CASI to paper SAQs. The computerized systems also eliminated errors in execution of "skip" instructions that occurred when subjects completed paper SAQs. In a number of instances, the computerized systems also appeared to encourage more complete reporting of sensitive behaviors such as use of illicit drugs. Among the two CASI systems, respondents rated Audio-CASI more favorably than Video-CASI in terms of interest, ease of use, and overall preference.     

Performances and negotiations: A case study of a wrestling referee

The experience of a wrestling referee is examined in terms of the performances and negotiations that take place. The author concludes that the role of referee sheds considerable light on the process of normative negotiations. The referee is responsible for maintaining social order in tenuous social situations. The audience's vision of the idealized sporting contest can never be realized. It is the referee's job to personally take on the inconsistencies and ambiguities of reality and to ritualistically transform the actual contest into the ordered contest they all desire.     

Transport schemes for topology-transparent scheduling

Transport protocols provide reliable, end-to-end communication between a source and a destination in a network. The Transmission Control Protocol (TCP) uses backward error correction, where the destination explicitly returns feedback to the source. Forward error correction (FEC) can also be used for transport; here the source includes enough redundancy in the encoding symbols to allow the destination to decode the message. In this paper, we compare the performance of two transport schemes, TCP and LT, a scheme based on rateless FEC codes, in a wireless ad hoc network when topology-transparent scheduling is used for channel access. These schedules are derived from cover-free families, a type of combinatorial design. They provide a mechanism to guarantee collision-free communication between any two nodes provided that each of the N nodes of the network has at most a specified number D of active (transmitting) neighbours. We find that LT outperforms TCP in more strenuous network conditions. To Frank Hwang on the occasion of his sixty-fifth birthday.     

An Evaluation of Routing and Volume-based Storage Policies in an Order Picking Operation

Order picking, the assembly of a customer's order from items in storage, is an essential link in the supply chain and is the major cost component of warehousing. The critical issue is to simultaneously reduce the cost and increase the speed of the order picking activity. This study departs from the limited prior research that focused on either routing of workers or storage of warehoused items. The main objectives are to (1) evaluate various routing heuristics versus an optimal routine in a volume-based storage environment, (2) propose several methods of implementing volume-based storage, and (3) examine the interaction of the routing and storage policies under different operating conditions of pick list size and demand skewness. The experimental results show statistically significant differences in the mean route distance for the routing policies, storage policies, and their interactions. Further testing indicates that the choice of certain routing and storage policies in combination can result in increased picking efficiency.