A century of t-tests

One hundred years ago, an author under the pseudonym of "Student" published a paper which was to become famous. It was entitled "The probable error of a mean". But what we now know as Student's t -test attracted little attention. It took another statistician of genius, R. A. Fisher, to amend, publicise and make it ubiquitous. But both Student's and Fisher's published versions were based upon faulty data. Stephen Senn reminds us of the third dedicated researcher and the quarter of a century delay before the story behind Student's t -test emerged.     

Sampling from compositional and directional distributions

This paper describes a method for sampling from a non-standard distribution which is important in both population genetics and directional statistics. Current approaches rely on complicated procedures which do not work well, if at all, in high dimensions and usual parameter set-ups. We use a Gibbs sampler which seems necessary in practical situations of high dimensions.     

The analysis of the AB/BA cross‐over trial in the medical literature

The evolution of opinion as to how to analyse the AB/BA cross‐over trials is described by examining the recommendations of three key papers. The impact of these papers on the medical literature is analysed by looking at citation rates as a function of various factors. It is concluded that amongst practitioners there is a highly imperfect appreciation of the issues raised by the possibility of carry‐over. Copyright © 2004 John Wiley & Sons, Ltd.     

Game theory and global environmental policy

Economists interpret global environmental quality to be a pure public good. Each country should contribute to its provision. However, this is hard to achieve because each government is tempted to take a free ride on the other governments’ efforts. Not only has this dilemma been analysed with game theoretical methods but game theory has also been used to think about how to make amends. This paper reviews the game theoretical discussion on how international policy frameworks may be designed to improve the chances for international cooperation. It is also shown that the evaluation of alternative environmental policy instruments deviates from the standard environmental economics model if applied to the international arena. For the benefit of an interdisciplinary readership, the evolution of the debate on global environmental policy is related to the recent history of economic thought. This history is taken to be materialised in the writings of economics’ Nobel Prize laureates.     

Blood Pressure Changes among Male Navaho Migrants to an Urban Environment

Des donnees comparatives sur la pression sanguine systolique et diastolique des Navahos de sexe masculin furent recueillies avant et apres leur emigration d'un milieu rural a un centre urbain. Les deux mesures furent significativement plus elevees apres l'emigration. Quelques facteurs causaux tels que le changement d'altitude, l'ingestion de gras satures et l'age furent elimines. D'un maniere pro-visoire, on conclut que des facteurs associes a l'emigration, tels qu'un changement dans les habitudes de repos, la pollution de l'air ainsi que la separation de la parente sont a l'origine de ces changements physiologiques.
Comparative data on systolic and diastolic blood pressures were obtained on male Navahos before and after migration from a rural to an urban environment. Both measures were significantly higher after migration. Various possible causes - such as change in altitude, saturated fat intake, and age - are eliminated. It is tentatively concluded that altered rest patterns, urban pollution, and separation from kin, i.e., things specific to the act of migration, are causally implicated.     

Estimating Benchmark Exposure for Air Particulate Matter Using Latent Class Models

We performed benchmark exposure (BME) calculations for particulate matter when multiple dichotomous outcome variables are involved using latent class modeling techniques and generated separate results for both the extra risk and additional risk. The use of latent class models in this study is advantageous because it combined several outcomes into just two classes (namely, a high‐risk class and a low‐risk class) and compared these two classes to obtain the BME levels. This novel approach addresses a key problem in risk estimation—namely, the multiple comparisons problem, where separate regression models are fitted for each outcome variable and the reference exposure will rely on the results of the best‐fitting model. Because of the complex nature of the estimation process, the bootstrap approach was used to estimate the reference exposure level, thereby reducing uncertainty in the obtained values. The methodology developed in this article was applied to environmental data by identifying unmeasured class membership (e.g., morbidity vs. no morbidity class) among infants in utero using observed characteristics that included low birth weight, preterm birth, and small for gestational age.     

Public Policy and Diffusion of Innovation

Marketers have traditionally studied diffusionof innovation with a primary focus on theindividual consumer as a unit of analysis, themajor types of findings being characteristicsof adopter categories and opinion leadership. We propose that this perspective is notadequate from a macromarketing perspective, inwhich the goals are to set public policy forsocietal good or to create an environment whichenables the diffusion of an innovation in a waythat no single marketer could do alone. Insetting public policy which can enable (orinhibit) diffusion of innovation for societalgood, a system composed of a mass socialinfrastructure, a competitive infrastructure,and a technical infrastructure should beconsidered.