Organisational Learning and Governance Through Embedded Practices

This article has two principal aims. The first is to reconcile thecompetence based approach to the firm with traditional contractualapproaches, instead of treating them as incompatible. The mainthesis advanced is that firms manage simultaneously competencesand transactions, but they do so in accordance with a specificlexicographic order of priorities. The second aim is to explorein detail the sources of knowledge formation in the firm. Theanalysis privileges anthropological readings which stress the roleof learning – both radical and incremental – within distributed communities of practice.     

Sticky Price Models of the Business Cycle: Can the Contract Multiplier Solve the Persistence Problem?

We construct a quantitative equilibrium model with firms setting prices in a staggered fashion and use it to ask whether monetary shocks can generate business cycle fluctuations. These fluctuations include persistent movements in output along with the other defining features of business cycles, like volatile investment and smooth consumption. We assume that prices are exogenously sticky for a short time. Persistent output fluctuations require endogenous price stickiness in the sense that firms choose not to change prices much when they can do so. We find that for a wide range of parameter values, the amount of endogenous stickiness is small. Thus, we find that in a standard quantitative model, staggered price‐setting, alone, does not generate business cycle fluctuations.     

Will they stay or will they go? How network properties of WebICs predict dropout rates of valuable Wikipedians

This paper contributes to our understanding of an increasingly prevalent work system, web-based internet communities (WebICs). We are particularly interested in how WebICs are governed given the fact how different they are compared to more classical forms of organization. We study the governance of a WebIC by studying the structure and dynamics of their edit network. Given the fact that the edit network is a relational structure, social network analysis is key to understanding these work systems. We demonstrate that characteristics of the edit network contribute to predicting the dropout hazard of valuable WebIC members. Since WebICs exist only thanks to the activity of their contributors, predicting drop-outs becomes crucial. The results show that reputation and controversy have different effects for different types of Wikipedians; i.e., an actor’s reputation decreases the dropout hazard of active Wikipedians, while participation on controversial pages decreases the dropout hazard of highly active Wikipedians.     

On edge orienting methods for graph coloring

We consider the problem of orienting the edges of a graph so that the length of a longest path in the resulting digraph is minimum. As shown by Gallai, Roy and Vitaver, this edge orienting problem is equivalent to finding the chromatic number of a graph. We study various properties of edge orienting methods in the context of local search for graph coloring. We then exploit these properties to derive four tabu search algorithms, each based on a different neighborhood. We compare these algorithms numerically to determine which are the most promising and to give potential research directions.     

Bayesian variable selection and regularization for time–frequency surface estimation

Summary.  We describe novel Bayesian models for time–frequency inverse modelling of non-stationary signals. These models are based on the idea of a Gabor regression , in which a time series is represented as a superposition of translated, modulated versions of a window function exhibiting good time–frequency concentration. As a necessary consequence, the resultant set of potential predictors is in general overcomplete—constituting a frame rather than a basis—and hence the resultant models require careful regularization through appropriate choices of variable selection schemes and prior distributions. We introduce prior specifications that are tailored to representative time series, and we develop effective Markov chain Monte Carlo methods for inference. To highlight the potential applications of such methods, we provide examples using two of the most distinctive time–frequency surfaces—speech and music signals—as well as standard test functions from the wavelet regression literature.     

A note on sample size savings with the use of a single well‐controlled clinical trial to support the efficacy of a new drug

In terms of the risk of making a Type I error in evaluating a null hypothesis of equality, requiring two independent confirmatory trials with two‐sided p‐values less than 0.05 is equivalent to requiring one confirmatory trial with two‐sided p‐value less than 0.001 25. Furthermore, the use of a single confirmatory trial is gaining acceptability, with discussion in both ICH E9 and a CPMP Points to Consider document. Given the growing acceptance of this approach, this note provides a formula for the sample size savings that are obtained with the single clinical trial approach depending on the levels of Type I and Type II errors chosen. For two replicate trials each powered at 90%, which corresponds to a single larger trial powered at 81%, an approximate 19% reduction in total sample size is achieved with the single trial approach. Alternatively, a single trial with the same sample size as the total sample size from two smaller trials will have much greater power. For example, in the case where two trials are each powered at 90% for two‐sided α=0.05 yielding an overall power of 81%, a single trial using two‐sided α=0.001 25 would have 91% power. Copyright © 2004 John Wiley & Sons, Ltd.     

Simulation for the complex Bingham distribution

The complex Bingham distribution is relevant for the shape analysis of landmark data in two dimensions. In this paper it is shown that the problem of simulating from this distribution reduces to simulation from a truncated multivariate exponential distribution. Several simulation methods are described and their efficiencies are compared.     

A continuous sampling plan using CUSUMs

A Continuous Sampling Plan, CSP-CUSUM, is proposed based on the use of Cumulative Sums (CUSUMs) for deciding when to switch between the phases of sampling inspection and 100% inspection. The Geometric CUSUM, also termed the Run-length CUSUM, is chosen for this purpose, and two separate CUSUMs are to be operated, one for each inspection phase. The conventional measures of performance for CSPs such as average outgoing quality, average fraction inspected, and average proportion passed under sampling inspection are evaluated for CSP-CUSUM, and comparisons with some standard CSPs are presented. An additional performance-measure, Average Cycle Length, is proposed. A table is provided to aid the choice of parameters for the operation of CSP-CUSUM. It is recommended that a Geometric CUSUM control chart be maintained in parallel with CSP-CUSUM to detect significant upward shifts in the incoming fraction defective.     

Urban versus Rural: Fertility Decline in the Cities and Rural Districts of Prussia, 1875 to 1910

Marital fertility in 54 Prussian cities and 407 Prussian Kreise (administrative areas) is analyzed using unusually rich and detailed socioeconomic and demographic data from eight quinquennial census between 1875 and 1910. Pooled cross-section time series methods are used to examine influences on marital fertility level and on marital fertility decline, focusing particularly on fertility differences according to level of urbanization. Increases in female labour force participation rate and income, the growth of financial services and communications, improvement in education, and reduction in infant mortality account for most of the marital fertility decline in 19th century Prussia. In 1875, rural and urban fertility were similar but by 1910, urban fertility was far lower than rural in part because the values of some of these variables changed more rapidly in the cities, and in part because some of these variables had stronger effects in urban settings.     

Statistical approaches for conducting network meta-analysis in drug development

We introduce health technology assessment and evidence synthesis briefly, and then concentrate on the statistical approaches used for conducting network meta-analysis (NMA) in the development and approval of new health technologies. NMA is an extension of standard meta-analysis where indirect as well as direct information is combined and can be seen as similar to the analysis of incomplete-block designs. We illustrate it with an example involving three treatments, using fixed-effects and random-effects models, and using frequentist and Bayesian approaches. As most statisticians in the pharmaceutical industry are familiar with SAS? software for analyzing clinical trials, we provide example code for each of the methods we illustrate. One issue that has been overlooked in the literature is the choice of constraints applied to random effects, and we show how this affects the estimates and standard errors and propose a symmetric set of constraints that is equivalent to most current practice. Finally, we discuss the role of statisticians in planning and carrying out NMAs and the strategy for dealing with important issues such as heterogeneity.