Quota fulfilment and errors in stratification

It is desired to draw a random sample containing specified numbers of individuals from each stratum of a population. First a random sample of size N is chosen from the whole populations and the stratum of each individual ascertained; then any shortfall is made up by selecting individuals with known stratum affiliation. Optimal values of N are sought allowing for cost structure and also the possibility of error in ascertaining the strata to which individuals in the first sample belong.     

Looking at Journals from Both Sides

The author, a professor in the field of communication, describes his contrasting experiences with publishing an open access society journal and advising a regional association in regards to turning over publication of its journal to a major commercial publishing firm. Using his experience of producing an open access journal as a foundation, he argues for the intrinsic importance of establishing credibility and exercising personal care in the production and maintenance of a journal. The author argues that current efforts by some societies to increase access to their journals through outsourcing to commercial publishers may be counterproductive to the fundamental goal of disseminating knowledge.     

Distribution and Poverty Impacts of Tax Structure Reform in Developing Countries: How Little We Know

The past two decades have witnessed widespread reforms of tax structures in developing countries. This article reviews available evidence on the effects of various taxes, and hence of tax structure reform, on distribution and the poor. Taxes on exports and goods consumed especially by the poor (e.g. kerosene) are the most consistently found to be regressive, whereas taxes on ‘luxury’ items such as cars, beverages and alcohol are the most likely to be progressive. Sales taxes are slightly more progressive, or less regressive, than taxes on imports. The reforms implemented are therefore unlikely to have worsened the effects of the tax structure on the poor.     

Estimates of human immunodeficiency virus prevalence and proportion diagnosed based on Bayesian multiparameter synthesis of surveillance data

Summary.  Estimates of the number of prevalent human immunodeficiency virus infections are used in England and Wales to monitor development of the human immunodeficiency virus–acquired immune deficiency syndrome epidemic and for planning purposes. The population is split into risk groups, and estimates of risk group size and of risk group prevalence and diagnosis rates are combined to derive estimates of the number of undiagnosed infections and of the overall number of infected individuals. In traditional approaches, each risk group size, prevalence or diagnosis rate parameter must be informed by just one summary statistic. Yet a rich array of surveillance and other data is available, providing information on parameters and on functions of parameters, and raising the possibility of inconsistency between sources of evidence in some parts of the parameter space. We develop a Bayesian framework for synthesis of surveillance and other information, implemented through Markov chain Monte Carlo methods. The sources of data are found to be inconsistent under their accepted interpretation, but the inconsistencies can be resolved by introducing additional 'bias adjustment' parameters. The best-fitting model incorporates a hierarchical structure to spread information more evenly over the parameter space. We suggest that multiparameter evidence synthesis opens new avenues in epidemiology based on the coherent summary of available data, assessment of consistency and bias modelling.     

D-optimal mixture component-amount designs for quadratic and cubic models

When the total amount of a mixture of ingredients needs to be taken into account (in addition to the composition of its ingredients), an experimental design requires several levels of the amount. Designs for such situations are discussed, and D-optimal choices are made for fitting quadratic and cubic models, for various numbers of experimental units.     

Inspection errors in graff-roeloffs modification of hierarchical dorfman screening procedures

Graff and Roeloffs' (1972) modification of the Dorfman (1943) screening procedure, and their analysis of the effects of inspection error on properties of the procedure, is extended to hierarchical procedures, using the results of Kotz and Johnson (1982).