bluuebunny/crossref_metadata_2025 huggingface dataset:
English departments in Chinese universities: purpose and function
Authors: Zhaoxiang Cheng
Published: March 2003

As a required subject from primary to graduate school, English has a special position in Chinese education. This special position is a mixed blessing for English departments in Chinese universities. It provides high–quality students in terms of English proficiency, while at the same time it overwhelms English studies as a specialist discipline with the demands of English language teaching (ELT) for non–majors and general learners. English studies aims at an understanding of the cultures/civilizations of the English–speaking peoples. It is a philosophical education in the way in which English–speaking peoples structure their knowledge, their literary/political/legal/economic thinking, as well as a comparative study between Chinese and English structures of knowledge. Rigorous training in their specialized field should first give English majors technical control over the material they handle, and then make them conscious of their limitations. Their discipline and training provide them with an instrument in their future work, and a habit, a frame of mind, and an awareness of methods and methodology. This training of potential specialists is therefore the basis of responsible citizenship, as academic rigor and discipline alert students to unreason in their society, and make them more amenable to a rational and efficient society. If ELT is going to survive as a university subject, it must take on the character of humanistic/philosophical education, though it should retain its technical aspects at the same time. While the training of specialists in English studies and of students in other disciplines will never be the same, both the English department and English language teaching in a university context must contribute to a humanistic education.
Teaching English literature in China: importance, problems and countermeasures
Authors: Qiping Yin , Shubo Chen
Published: March 2003

This paper seeks to argue for the importance of teaching literature in English departments in Chinese universities. The past two decades in China have heard ever–increasing outcries for making English courses ‘more pragmatic’, a policy which threatens to marginalize and even banish literature. Behind such a phenomenon lurks a prevalent assumption: that English education is a matter of ingesting information, of mastering techniques, and of acquiring facts and know–how, whereas literature is a soft option, an indulgence or a mere trimming to decorate the hard center of the market–oriented syllabus. In order to counter such a trend, we need first of all to address the following theoretical issues: What is the primary task of an English department in China? Is the teaching of English literature relevant to the Chinese market economy today? If yes, in what way is it relevant? How does one persuade a member of modern Chinese society that there is a profit in reading, say, Chaucer and Shakespeare, in harkening to any non–Chinese and, ‘worse’, non–modern non–Chinese voices? In answering those questions, the present paper suggests a number of countermeasures to combat those policies promoting a shallow ‘pragmatism’ in English teaching in China today.
Income Distribution, Taxation, and the Private Provision of Public Goods
Authors: Itaya Jun‐Ichi , De Meza David , Myles Gareth D.
Published: March 2003

This article investigates the role of taxation when public goods are privately provided. Externalities between consumers via the public good are shown to cause kinks in social indifference curves. As a result, a government restricted to income taxation should engineer enough inequality to ensure there are some non‐contributors to the public good. Whether commodity taxation changes this conclusion depends on the extent to which consumers “see through” the government budget constraint. If they can, inequality should still be sought. When they cannot, in contrast to the case of an economy with only private goods, commodity taxation can be used in conjunction with income transfers to achieve the first‐best.
Debt Neutrality and the Infinite–Lived Representative Consumer
Authors: Crettez Bertrand , Michel Philippe , Wigniolle Bertrand
Published: March 2003

In this paper, we study the intertemporal equilibria of an infinite–lived representative agent model with public debt. We show that for a given path of government expenditures, there generally exists a continuum of equilibria depending on various debt policies. These equilibria are characterized by different paths of consumption and leisure. Two examples illustrate the results: in the first one consumption and leisure may converge to zero, in the second one consumption goes to infinity while leisure goes to its maximum value. In a third example with externalities à la Romer, the standard intertemporal equilibrium with zero public debt may be dominated by other intertemporal equilibria.
Probabilistic Darwinism: Louis Agassiz vs. Asa Gray on Science, Religion, and Certainty
Authors: Croce Paul Jerome
Published: March 2003

Despite the professed harmony of science and religion in early to middle nineteenth‐century culture, scientific practice gradually veered away from confirmation of religious assumptions. This trend culminated in the shock of Charles Darwin's theory of species development, which troubled many scientists and religious believers both for its explicit naturalism and for the unprovable probabilism at the heart of its method. Two key players — and antagonists — in the reception of Darwinism in America, Louis Agassiz and Asa Gray, actually agreed in their assessment of the probabilistic quality of Darwinism, but they split over how much uncertainty to wel‐come into their science and their religion. Agassiz became intellectually marginalized because he continued to demand certainty, while Gray’s acceptance of uncertainty represented a growing trend among intellectuals of science and religion.
Hypertext reading: novice vs. expert reading
Authors: Kumbruck Christel
Published: March 2003

This paper discusses some differences between linear reading and reading in hypertext, a non‐linear medium. The investigations of hypertext form part of a research project on the design and use of multimedia systems, and hypertext in particular, for assessing planning applications for large scale building developments, such as chemical plants which are subject to the Air Pollution Laws (Immissionsschutzgesetz). The key question treated here is whether hypertext makes it easier to read and assess such planning applications for experts (officials of the regional government and advisers to interest groups) and for lay people who may be objectors (such as members of ecology groups or those living in the neighbourhood). The development and testing of a hypertext system for this purpose involves considering the literature in psychology on cognitive differences between reading conventional and hypertext documents and on advantages and disadvantages of hypertext. From the literature review and from interview data, it is concluded that hypertext has fewer benefits in this situation than it appears to promise; while there are some advantages for experts, who nevertheless also need to apply conventional reading strategies to conventional paper texts, it is of limited use to the lay non‐experts who have an interest in planning inquiries.
An investigation of hierarchical relationships in children’s literacy attainments at baseline
Authors: Sainsbury Marian , Schagen Ian , Whetton Chris , Caspall Louise
Published: March 2003

This paper describes one element of the research basis for the Baseline Assessment Scales now published for optional use in baseline schemes nationally (SCAA, 1997a). The aim in developing these scales was to provide a range of criteria that would allow almost all children to show some attainment, whilst also acknowledging the attainments of the most able. For this purpose, four‐point scales were required. The first point would be attainable by over 80 per cent of children in their first term of school, and the fourth by only 20 per cent or fewer, with two intermediate points. Four such scales were trialled for reading, and one for writing. As part of the trial analysis, an investigation was undertaken into the hierarchies amongst the items on each scale – that is, to what extent was it possible for a child to attain a more difficult item, whilst failing an easier item on the same scale? A ‘coefficient of dependency’ was calculated for each pair of items on each scale. The percentages of children achieving each item are reported, and the strength of the hierarchies amongst them. This provides some evidence as to the interrelationships between children’s literacy attainments at the start of school.
The effect of visual imagery training on the reading and listening comprehension of low listening comprehenders in Year 2
Authors: Center Yola , Freeman Louella , Robertson Gregory , Outhred Lynne
Published: March 2003

A study was carried out to assess the effectiveness of a representational visual imagery training programme on the reading and listening comprehension of a group of poor listening comprehenders in Year 2 (mean age: 7 years 8 months). Results indicated that relative to a matched control group, the experimental group improved significantly on a curriculum‐based test of listening comprehension, a standardised test of reading comprehension and a measure of story event structure, with results approaching significance on an adapted test of listening comprehension. The implications of the results for early institution of visual imagery training in the context of listening comprehension instruction are discussed.
Environmental print and word reading
Authors: Cronin Virginia , Farrell Denise , Delaney Mary
Published: March 2003

The nature of the earliest stage of reading was examined by comparing two views about the importance of environmental print in children’s learning experiences. One theory holds that environmental print leads to the acquisition of reading through developing rudimentary representations of specific words and logos, while the second theory concerns assembled phonology and asserts that reading begins with knowing letters and their sounds. Supporters of this theory hold that knowledge of environmental print and logos is reading the environment and may not directly facilitate the acquisition of word reading. Two studies were conducted with non‐reading preschool children in which environmental print knowledge was assessed and related to word recognition training. In the first session of each study children were presented with accurate representations of environmental print and logos such as ‘McDonalds’ and ‘Stop’ to find the ones they were able to identify and the ones they failed to identify. In the second session learning trials were conducted with those words from the logos that the children identified and also those that they failed to identify and with matching control words. Both studies found that the words from the known logos were more readily learned than the matching control words, but only in Study 1 were the known logo words learned more readily than the ones the children did not know. The results were discussed in terms of Gibson’s (1969) theory of perceptual learning, and supported the view that environment print and logo knowledge facilitated word reading.
Rhymes are important: a comment on Savage
Authors: Goswami Usha
Published: March 2003

Savage (2001) makes 3 basic claims about the scientific database concerning rhyme and analogy in reading. The first is that the relationship between rhyme and reading remains controversial. The second is that there is doubt about the relevance of children’s ability to make orthographic analogies for classroom reading instruction. The third is that training studies in reading have shown that rhyme is not important. These claims are considered in the current paper.
The use of tinted lenses to alleviate reading difficulties
Authors: Whiteley Helen , Smith Chris
Published: March 2003

An increasing number of optometrists are offering assessments using the Intuitive Colorimeter (Wilkins, Nimmo‐Smith and Jansons, 1992) to determine whether children who have reading difficulties might benefit from the use of tinted lenses. Suggestions have been made in the media that tinted lenses may provide a ‘cure’ for developmental dyslexia, and there have been many anecdotal accounts of improvements in reading following their use (e.g. Brace, 1993). However, such extreme claims are not typical of the scientific literature supporting the use of tinted lenses. This article provides an overview of the research into the use of tinted lenses for the amelioration of reading difficulties. The electronic databases searched for this review were BIDS, MEDLINE, PsychInfo, PsychLit and Science Direct. Key search terms used were coloured (colored) lenses, Irlen lenses, scotopic sensitivity and visual deficits in combination with the term ‘reading difficulties’.
Parent–child pre–school activities can affect the development of literacy skills
Authors: Wood Clare
Published: March 2003

This paper considers the nature of joint (parent–child) pre–school activities in the home, and their potential to contribute to the development of early reading skills. Parents gave details of the nature and frequency of any play–based activities that they routinely completed with their children. Their children were assessed on various aspects of phonological awareness, as well as their receptive vocabulary and short–term memory at four years old. One year later they completed a similar battery that also included measures of reading and spelling ability. Children who engaged in a variety of pre–school, parent–child activities showed the best achievement in reading one year later. The frequency of joint activities was also found to impact on reading attainment, vocabulary, memory and aspects of phonological awareness. The importance of shared storybook reading for later independent reading ability was reiterated by this study.
Identifying dyslexia in multilingual students: can phonological awareness be assessed in the majority language?
Authors: Miller Guron Louise , Lundberg Ingvar
Published: March 2003

A study of 97 students from two schools in Göteborg, Sweden, examined reading proficiency and phonological skill using a comprehensive battery of group measures in the classroom. The sample comprised 38 monolingual native‐Swedish speakers, and 59 multilingual students for whom Swedish is an additional language. Students were administered tests of non‐verbal intelligence, vocabulary, reading comprehension, word recognition and non‐vocal phonological tasks. Two sub‐groups of 26 monolingual and 26 multilingual students, matched on non‐verbal intelligence, also participated in oral word and nonword reading tasks. No significant differences were found between language groups on the separate phonological subtests or the composite phonological score after controlling for non‐verbal intelligence in hierarchical regression analyses. The language groups were equally represented at the 20th percentile on both composite phonology and word reading measures. The composite phonological score was equally powerful for both language groups in predicting word recognition. The results of the present study suggest that, given sufficient exposure to the majority language, it is possible to assess a range of phonological skills among speakers of minority languages using the same battery of tasks as for native speakers.
Design of Human Immunodeficiency Virus Intervention Trials in Developing Countries
Authors: Hayes R.
Published: March 2003

Randomized controlled trials are recognized as the ‘gold standard’ for evaluating the effect of health interventions, yet few such trials of human immunodeficiency virus (HIV) preventive interventions have been conducted. We discuss the role of randomized trials in the evaluation of such interventions, and we review the strengths and weaknesses of this and other approaches. Randomization of clusters (groups of individuals) may sometimes be appropriate, and we discuss several issues in the design of such cluster-randomized trials, including sample size, the definition and size of clusters, matching and the role of base-line data. Finally we review some general issues in the design of HIV prevention trials, including the choice of the study population, trial end points and ethical issues. It is argued that randomized trials have an important role to play in the evolution of HIV control.
The Zero-Inflated Poisson Model and the Decayed, Missing and Filled Teeth Index in Dental Epidemiology
Authors: Böhning Dankmar , Dietz E. , Schlattmann P. , Mendonça L. , Kirchner U.
Published: March 2003

For frequency counts, the situation of extra zeros often arises in biomedical applications. This is demonstrated with count data from a dental epidemiological study in Belo Horizonte (the Belo Horizonte caries prevention study) which evaluated various programmes for reducing caries. Extra zeros, however, violate the variance–mean relationship of the Poisson error structure. This extra-Poisson variation can easily be explained by a special mixture model, the zero-inflated Poisson (ZIP) model. On the basis of the ZIP model, a graphical device is presented which not only summarizes the mixing distribution but also provides visual information about the overall mean. This device can be exploited to evaluate and compare various groups. Ways are discussed to include covariates and to develop an extension of the conventional Poisson regression. Finally, a method to evaluate intervention effects on the basis of the ZIP regression model is described and applied to the data of the Belo Horizonte caries prevention study.
A Comparison of Population Average and Random-Effect Models for the Analysis of Longitudinal Count Data with Base-Line Information
Authors: Crouchley R. , Davies R. B.
Published: March 2003

The generalized estimating equation (GEE) approach to the analysis of longitudinal data has many attractive robustness properties and can provide a ‘population average’ characterization of interest, for example, to clinicians who have to treat patients on the basis of their observed characteristics. However, these methods have limitations which restrict their usefulness in both the social and the medical sciences. This conclusion is based on the premise that the main motivations for longitudinal analysis are insight into microlevel dynamics and improved control for omitted or unmeasured variables. We claim that to address these issues a properly formulated random-effects model is required. In addition to a theoretical assessment of some of the issues, we illustrate this by reanalysing data on polyp counts. In this example, the covariates include a base-line outcome, and the effectiveness of the treatment seems to vary by base-line. We compare the random-effects approach with the GEE approach and conclude that the GEE approach is inappropriate for assessing the treatment effects for these data.
Statistical Review by Research Ethics Committees
Authors: Williamson P. , Hutton J. L. , Bliss J. , Blunt J. , Campbell M. J. , Nicholson R.
Published: March 2003

This paper discusses some of the issues surrounding statistical review by research ethics committees (RECs). A survey of local RECs in 1997 revealed that only 27/184 (15%) included a statistician member at that time, although 70/175 (40%) recognized the need for such. The role of the statistician member is considered and the paper includes a summary of a meeting of the Royal Statistical Society to discuss statistical issues that frequently arise in the review of REC applications. A list of minimum qualifications which RECs should expect from anyone claiming to be a statistician would be useful, together with a list of statisticians who are well qualified and willing to serve on RECs, and a list of training courses for REC members covering the appropriate statistical issues.
Theoretical and Practical Issues in Purchasing Power Parities Illustrated with Reference to the 1993 Organization for Economic Co-Operation and Development Data
Authors: Cuthbert James R.
Published: March 2003

This paper deals first with some theoretical issues in purchasing power parities, including the definition of a generalized class of additive indices, which includes the standard Geary–Khamis and Iklé indices as special cases, and the definition of indicators of price and quantity structure which are independent of the particular units in which quantities are originally expressed. The paper then provides a comparative analysis of the results of applying these techniques to the 1993 Organization for Economic Co-operation and Development data and relates the results to underlying features of the price and expenditure data.
Overcoming Biases and Misconceptions in Ecological Studies
Authors: Guthrie Katherine A. , Sheppard Lianne
Published: March 2003

The aggregate data study design provides an alternative group level analysis to ecological studies in the estimation of individual level health risks. An aggregate model is derived by aggregating a plausible individual level relative rate model within groups, such that population-based disease rates are modelled as functions of individual level covariate data. We apply an aggregate data method to a series of fictitious examples from a review paper by Greenland and Robins which illustrated the problems that can arise when using the results of ecological studies to make inference about individual health risks. We use simulated data based on their examples to demonstrate that the aggregate data approach can address many of the sources of bias that are inherent in typical ecological analyses, even though the limited between-region covariate variation in these examples reduces the efficiency of the aggregate study. The aggregate method has the potential to estimate exposure effects of interest in the presence of non-linearity, confounding at individual and group levels, effect modification, classical measurement error in the exposure and non-differential misclassification in the confounder.
Estimation in Epidemics with Incomplete Observations
Authors: Becker Niels G. , Hasofer Abraham M.
Published: March 2003

The construction of estimating equations by martingale methods is generalized to yield estimators with explicit expressions for the parameters of the birth-and-death and the general epidemic processes when only partial observations are available. (For the birth-and-death process the death process is observed but the number of births is observed only at the end and for the general epidemic process only the removal process is observed.) For large populations, the use of the martingale central limit theorem yields asymptotic confidence regions for the parameters. Explicit expressions are derived for estimators of the variances of the large sample distributions. The range of validity and usefulness of the new estimators is determined by simulation.
Simpson’s Paradox and the Bayes Factor
Authors: Aitkin Murray
Published: March 2003

A counter-example presented by Lindley to Aitkin’s posterior Bayes factor is examined. The paradoxical feature of the counter-example is found to be a simple case of Simpson’s paradox.
Limited Information Likelihood Analysis Of Survey Data
Authors: Chambers Raymond L. , Dorfman Alan H. , Wang Suojin
Published: March 2003

Analysts of survey data are often interested in modelling the population process, or superpopulation, that gave rise to a ‘target’ set of survey variables. An important tool for this is maximum likelihood estimation. A survey is said to provide limited information for such inference if data used in the design of the survey are unavailable to the analyst. In this circumstance, sample inclusion probabilities, which are typically available, provide information which needs to be incorporated into the analysis. We consider the case where these inclusion probabilities can be modelled in terms of a linear combination of the design and target variables, and only sample values of these are available. Strict maximum likelihood estimation of the underlying superpopulation means of these variables appears to be analytically impossible in this case, but an analysis based on approximations to the inclusion probabilities leads to a simple estimator which is a close approximation to the maximum likelihood estimator. In a simulation study, this estimator outperformed several other estimators that are based on approaches suggested in the sampling literature.
Fractal Analysis of Surface Roughness by Using Spatial Data
Authors: Davies S. , Hall Peter
Published: March 2003

We develop fractal methodology for data taking the form of surfaces. An advantage of fractal analysis is that it partitions roughness characteristics of a surface into a scale-free component (fractal dimension) and properties that depend purely on scale. Particular emphasis is given to anisotropy where we show that, for many surfaces, the fractal dimension of line transects across a surface must either be constant in every direction or be constant in each direction except one. This virtual direction invariance of fractal dimension provides another canonical feature of fractal analysis, complementing its scale invariance properties and enhancing its attractiveness as a method for summarizing properties of roughness. The dependence of roughness on direction may be explained in terms of scale rather than dimension and can vary with orientation. Scale may be described by a smooth periodic function and may be estimated nonparametrically. Our results and techniques are applied to analyse data on the surfaces of soil and plastic food wrapping. For the soil data, interest centres on the effect of surface roughness on retention of rain-water, and data are recorded as a series of digital images over time. Our analysis captures the way in which both the fractal dimension and the scale change with rainfall, or equivalently with time. The food wrapping data are on a much finer scale than the soil data and are particularly anisotropic. The analysis allows us to determine the manufacturing process which produces the smoothest wrapping, with least tendency for micro-organisms to adhere.
Polynomial Regression and Estimating Functions in the Presence of Multiplicative Measurement Error
Authors: Iturria Stephen J. , Carroll Raymond J. , Firth David
Published: March 2003

We consider the polynomial regression model in the presence of multiplicative measurement error in the predictor. Two general methods are considered, with the methods differing in their assumptions about the distributions of the predictor and the measurement errors. Consistent parameter estimates and asymptotic standard errors are derived by using estimating equation theory. Diagnostics are presented for distinguishing additive and multiplicative measurement error. Data from a nutrition study are analysed by using the methods. The results from a simulation study are presented and the performances of the methods are compared.
Saddlepoint Approximations for the Difference of Order Statistics and Studentized Sample Quantiles
Authors: Ma Chunsheng , Robinson John
Published: March 2003

For a sample from a given distribution the difference of two order statistics and the Studentized quantile are statistics whose distribution is needed to obtain tests and confidence intervals for quantiles and quantile differences. This paper gives saddlepoint approximations for densities and saddlepoint approximations of the Lugannani–Rice form for tail probabilities of these statistics. The relative errors of the approximations are n  −1 uniformly in a neighbourhood of the parameters and this uniformity is global if the densities are log-concave.
A Goodness-of-fit Test for Exponentiality Based on the Memoryless Property
Authors: Ahmad Ibrahim A. , Alwasel Ibrahim A.
Published: March 2003

In this investigation a test of goodness of fit for exponentiality is proposed. This procedure applies equally whether the scale and/or the location parameters of the distribution are known or not. The limiting null and non-null distributions of the test statistic are normal under minimal conditions. Monte Carlo critical values for small sample sizes are given and the power of the test is calculated for various alternatives showing that it compares favourably relatively to other more complicated published procedures.
Extensions of Fill's Algorithm for Perfect Simulation
Authors: Møller Jesper , Schladitz Katja
Published: March 2003

Fill's algorithm for perfect simulation for attractive finite state space models, unbiased for user impatience, is presented in terms of stochastic recursive sequences and extended in two ways. Repulsive discrete Markov random fields with two coding sets like the auto-Poisson distribution on a lattice with 4-neighbourhood can be treated as monotone systems if a particular partial ordering and quasi-maximal and quasi-minimal states are used. Fill's algorithm then applies directly. Combining Fill's rejection sampling with sandwiching leads to a version of the algorithm which works for general discrete conditionally specified repulsive models. Extensions to other types of models are briefly discussed.
The Exact Bootstrap Mean and Variance of an L-estimator
Authors: Hutson Alan D. , Ernst Michael D.
Published: March 2003

Exact analytic expressions for the bootstrap mean and variance of any L-estimator are obtained, thus eliminating the error due to bootstrap resampling. The expressions follow from the direct calculation of the bootstrap mean vector and covariance matrix of the whole set of order statistics. By using these expressions, recommendations can be made about the appropriateness of bootstrap estimation under given conditions.
Maximum Entropy Sampling and Optimal Bayesian Experimental Design
Authors: Sebastiani Paola , Wynn Henry P.
Published: March 2003

When Shannon entropy is used as a criterion in the optimal design of experiments, advantage can be taken of the classical identity representing the joint entropy of parameters and observations as the sum of the marginal entropy of the observations and the preposterior conditional entropy of the parameters. Following previous work in which this idea was used in spatial sampling, the method is applied to standard parameterized Bayesian optimal experimental design. Under suitable conditions, which include non-linear as well as linear regression models, it is shown in a few steps that maximizing the marginal entropy of the sample is equivalent to minimizing the preposterior entropy, the usual Bayesian criterion, thus avoiding the use of conditional distributions. It is shown using this marginal formulation that under normality assumptions every standard model which has a two-point prior distribution on the parameters gives an optimal design supported on a single point. Other results include a new asymptotic formula which applies as the error variance is large and bounds on support size.
Mixture Kalman Filters
Authors: Chen Rong , Liu Jun S.
Published: March 2003

In treating dynamic systems, sequential Monte Carlo methods use discrete samples to represent a complicated probability distribution and use rejection sampling, importance sampling and weighted resampling to complete the on-line ‘filtering’ task. We propose a special sequential Monte Carlo method, the mixture Kalman filter, which uses a random mixture of the Gaussian distributions to approximate a target distribution. It is designed for on-line estimation and prediction of conditional and partial conditional dynamic linear models, which are themselves a class of widely used non-linear systems and also serve to approximate many others. Compared with a few available filtering methods including Monte Carlo methods, the gain in efficiency that is provided by the mixture Kalman filter can be very substantial. Another contribution of the paper is the formulation of many non-linear systems into conditional or partial conditional linear form, to which the mixture Kalman filter can be applied. Examples in target tracking and digital communications are given to demonstrate the procedures proposed.
On Expected Volumes of Multidimensional Confidence Sets Associated With the Usual and Adjusted Likelihoods
Authors: Datta Gauri S. , DiCiccio Thomas J.
Published: March 2003

We consider a general multiparameter set-up, where both the interest and the nuisance parameters are possibly vector valued. We derive an explicit higher order asymptotic formula to compare the expected volumes of confidence sets given by likelihood ratio statistics arising from the usual profile likelihood and various adjustments thereof. Our general framework also allows us to include highest posterior density regions, with approximate frequentist validity, in the study. The fact that our interest parameter is possibly vector valued complicates the derivation and warrants the development of special tools and techniques.
A Risk Set Calibration Method for Failure Time Regression by Using a Covariate Reliability Sample
Authors: Xie Sharon X. , Wang C. Y. , Prentice Ross L.
Published: March 2003

Regression parameter estimation in the Cox failure time model is considered when regression variables are subject to measurement error. Assuming that repeat regression vector measurements adhere to a classical measurement model, we can consider an ordinary regression calibration approach in which the unobserved covariates are replaced by an estimate of their conditional expectation given available covariate measurements. However, since the rate of withdrawal from the risk set across the time axis, due to failure or censoring, will typically depend on covariates, we may improve the regression parameter estimator by recalibrating within each risk set. The asymptotic and small sample properties of such a risk set regression calibration estimator are studied. A simple estimator based on a least squares calibration in each risk set appears able to eliminate much of the bias that attends the ordinary regression calibration estimator under extreme measurement error circumstances. Corresponding asymptotic distribution theory is developed, small sample properties are studied using computer simulations and an illustration is provided.
The Construction of Efficient Two-Replicate Row–Column Designs for Use in Field Trials
Authors: John J. A. , Williams E. R.
Published: March 2003

Two-replicate row–column designs are often used for field trials in multisite tree or plant breeding programmes. With only two replicates for each trial, it is important to use designs with optimal or near optimal efficiency factors. This paper presents an algorithm for generating such designs. The method extends the contraction approach of Bailey and Patterson to any set of parameters and uses the factorial design construction algorithm of Williams and John to generate designs. Our experience with the algorithm is that it produces designs that are at least as good as, and often much better and more quickly generated than, those obtained by other recent computer algorithms.
Confocal Fluorescence Microscopy of Leaf Cells: An Application of Bayesian Image Analysis
Authors: Hurn M.
Published: March 2003

Confocal fluorescence microscopy is a recent and important imaging tool for visualizing three-dimensional specimens without the need for physical sectioning, so that changes in living cells can be studied over time. The application of interest here is a study of the changes in the stomatal guard cells of plant leaves during their opening and closing response sequences. Quantitative estimates of the size and shape of these cells rely on accurate classification (or segmentation) of the images into areas which are parts of cells and areas which are background. This segmentation is complicated in confocal microscopy because the images appear to be ‘smudged’ or ‘dirty’; this degradation is due largely to diffraction and attenuation of the recorded signal caused by the specimen itself. Correcting for this degradation is difficult without knowing the specimen-dependent parameters involved in the degradation process. A fully Bayesian approach is proposed for tackling this problem of blind deconvolution, i.e. of concurrently estimating the degradation parameters while segmenting two-dimensional sections. The end-products are interval estimates of size and shape which acknowledge some of the uncertainty involved in the segmentation. The results are promising, generating credible intervals which are sufficiently narrow to be useful in practice.
Frequency Domain Log-linear Models; Air Pollution and Mortality
Authors: Kelsall Julia E. , Zeger Scott L. , Samet Jonathan M.
Published: March 2003

Motivated by a study of the association between counts of daily mortality and air pollution, we present a frequency domain estimation approach for log-linear models that accounts for both overdispersion and autocorrelation. The methods also allow for the discounting or downweighting of information at particular frequencies at which, for example, confounding variables are likely to have greatest influence. This allows flexible sensitivity analyses to be carried out to assess the possible effect of confounders on the estimated effect. We apply the methods to estimate the association between counts of mortality and the concentration of airborne particles in Philadelphia, USA, for the years 1974–1988. We obtain an estimated effect of particulate air pollution on mortality that is significantly greater than zero but less than that obtained by a standard log-linear analysis.
Analyses of Infectious Disease Data from Household Outbreaks by Markov Chain Monte Carlo Methods
Authors: O’Neill Philip D. , Balding David J. , Becker Niels G. , Eerola Mervi , Mollison Denis
Published: March 2003

The analysis of infectious disease data presents challenges arising from the dependence in the data and the fact that only part of the transmission process is observable. These difficulties are usually overcome by making simplifying assumptions. The paper explores the use of Markov chain Monte Carlo (MCMC) methods for the analysis of infectious disease data, with the hope that they will permit analyses to be made under more realistic assumptions. Two important kinds of data sets are considered, containing temporal and non-temporal information, from outbreaks of measles and influenza. Stochastic epidemic models are used to describe the processes that generate the data. MCMC methods are then employed to perform inference in a Bayesian context for the model parameters. The MCMC methods used include standard algorithms, such as the Metropolis–Hastings algorithm and the Gibbs sampler, as well as a new method that involves likelihood approximation. It is found that standard algorithms perform well in some situations but can exhibit serious convergence difficulties in others. The inferences that we obtain are in broad agreement with estimates obtained by other methods where they are available. However, we can also provide inferences for parameters which have not been reported in previous analyses.
Case–Control Studies with Complex Sampling
Authors: Scott Alastair , Wild Chris
Published: March 2003

The use of complex sampling designs in population-based case–control studies is becoming more common, particularly for sampling the control population. This is prompted by all the usual cost and logistical benefits that are conferred by multistage sampling. Complex sampling has often been ignored in analysis but, with the advent of packages like SUDAAN, survey-weighted analyses that take account of the sample design can be carried out routinely. This paper explores this approach and more efficient alternatives, which can also be implemented by using readily available software.
Estimation of Origin–Destination Trip Rates in Leicester
Authors: Hazelton Martin L.
Published: March 2003

The road system in region RA of Leicester has vehicle detectors embedded in many of the network’s road links. Vehicle counts from these detectors can provide transportation researchers with a rich source of data. However, for many projects it is necessary for researchers to have an estimate of origin-to-destination vehicle flow rates. Obtaining such estimates from data observed on individual road links is a non-trivial statistical problem, made more difficult in the present context by non-negligible measurement errors in the vehicle counts collected. The paper uses road link traffic count data from April 1994 to estimate the origin–destination flow rates for region RA. A model for the error prone traffic counts is developed, but the resulting likelihood is not available in closed form. Nevertheless, it can be smoothly approximated by using Monte Carlo integration. The approximate likelihood is combined with prior information from a May 1991 survey in a Bayesian framework. The posterior is explored using the Hastings–Metropolis algorithm, since its normalizing constant is not available. Preliminary findings suggest that the data are overdispersed according to the original model. Results for a revised model indicate that a degree of overdispersion exists, but that the estimates of origin–destination flow rates are quite insensitive to the change in model specification.
Markov Chain Monte Carlo Inference Applied to a Complex Model for the Longitudinal Analysis of Breast Patterns
Authors: Myles Jonathan P. , Duffy Stephen W. , Prevost Teresa C. , Day Nicholas E. , Hakama Matti , Salminen Tiina
Published: March 2003

As part of a recently completed study of the effectiveness of breast cancer screening in Finland, 3975 women were invited to attend screens at 2-yearly intervals and the screens were classified as ‘favourable' or ‘unfavourable' in a simplification of the Wolfe classification of mammographic patterns. There is interest in both the rate of change from favourable to unfavourable states and vice versa, and the error rates involved in classifying patterns, in particular in whether these vary with age. We discuss simplifying assumptions which need to be made, because of the very short time series that is involved (four or five observations), to enable transitions between states to be disentangled from classification errors. A model for the data is proposed, the likelihood for the data given this model is obtained and a Markov chain Monte Carlo method is used to obtain posterior distributions. We show how our estimation procedure was checked in advance of the availability of the data, by means of a simulation.
Correcting for Non-Compliance Bias in Case–Control Studies to Evaluate Cancer Screening Programmes
Authors: Duffy Stephen W. , Cuzick Jack , Tabar Laszlo , Vitak Bedrich , Chen Tony Hsiu-Hsi , Yen Ming-Fang , Smith Robert A.
Published: March 2003

In the evaluation of uncontrolled service screening programmes for cancer, the case–control design is sometimes used, in which people who die from the disease in question are compared with live controls with respect to screening histories. Such a design tends to yield estimates of relative mortality in voluntary participants compared with non-participants. This may bias results, since compliers and non-compliers may differ a priori in ways which are not related to screening but which nevertheless affect the risk of death from the disease. We present a simple method, employing external data from previously published randomized controlled trials of screening, of correction for this bias. We illustrate it by using data from a case–control study performed within the invited arm of the Malmö mammographic screening trial, a prospective study from the service screening programme in two counties in Sweden, and a matched case–control study of mammographic screening in Florence, Italy.
AN OPTIMALITY CRITERION FOR AGGREGATING A SET OF TIME SERIES IN A COMPOSITE INDEX
Authors: Baragona R. , Carlucci F.
Published: March 2003

Linear combination is a common feature of most methods designed to aggregate a set of time series into a composite index. In this paper the principal components approach is utilized by means of spectral techniques to improve the variance explained by the first principal component. The optimality criterion resorts to the alignment of the elements of the vector time series.
Goodness‐of‐fit tests for autoregressive processes
Authors: Anderson T. W.
Published: March 2003

Goodness‐of‐fit tests for autoregressive processes can be based on the difference betwe en the empirical standardized spectral distribution of an observed time series and the standardized spectral distribution of the autoregressive process with parameters estimated from the series. The asymptotic covariance function of this difference, considered as a stochastic process on [0, π], is found. Methods to compute the asymptotic distribution of the Cramer‐‐von Mises statistic are given.
A note on L1 density estimation for linear processes
Authors: Datta Somnath
Published: March 2003

In this paper, we consider the L1 performance of a kernel estimator, f^n of the density of a linear process Xt∑∞k=0akZt−k, a0 = 1, where {Zt} is a sequence of independent and identically distributed (i.i.d.) random variables with E|Z1|ε< ∞, for some ε > 1, and {ak} is a sequence of reals converging to zero at a certain rate. Asymptotic minimizations of the integrated L1 risk of fn and its upper bounds are considered. This paper extends the earlier results for the i.i.d. case by Devroye and Gyorfi (Nonparametric Density Estimation: The L1 View. New York: Wiley, 1985) and by Hall and Wand (Minimizing the L1 distance in nonparametric density estimation, J. Multivariate Anal.26 (1988), 59–88) to the linear process case. Numerical examples to illustrate the performance of fn are also presented.
Tracking abrupt frequency changes
Authors: Li Ta‐Hsin , Kedem Benjamin
Published: March 2003

This paper addresses the problem of accurate estimation and rapid adaptation of abrupt frequency changes from noisy sinusoidal signals. A two‐filter adaptive algorithm is proposed to achieve the seemingly contradictory objectives. This algorithm is derived from an iterative batch procedure that has been proved to yield consistent and asymptotically Gaussian estimates for constant‐frequency estimation. These properties provide a basis for the detection of abrupt changes in the time‐varying frequency. Combining the high accuracy of narrow‐band/long‐memory filtering with the high adaptability of wide‐band/short‐memory filtering, the two‐filter approach is particularly suitable for tracking time‐varying frequencies that can be approximately modeled as piecewise‐constant functions of time. Simulation results are reported that justify the viability of the method.
Bayesian analysis of autoregressive fractionally integrated moving‐average processes
Authors: Pai Jeffrey S. , Ravishanker Nalini
Published: March 2003

For the autoregressive fractionally integrated moving‐average (ARFIMA) processes which characterize both long‐memory and short‐memory behavior in time series, we formulate Bayesian inference using Markov chain Monte Carlo methods. We derive a form for the joint posterior distribution of the parameters that is computationally feasible for repetitive evaluation within a modified Gibbs sampling algorithm that we employ. We illustrate our approach through two examples.
Long‐range Dependence: Revisiting Aggregation with Wavelets
Authors: Abry Patrice , Veitch Darryl , Flandrin Patrick
Published: March 2003

The aggregation procedure is a natural way to analyse signals which exhibit long‐range‐dependent features and has been used as a basis for estimation of the Hurst parameter, H. In this paper it is shown how aggregation can be naturally rephrased within the wavelet transform framework, being directly related to approximations of the signal in the sense of a Haar multiresolution analysis. A natural wavelet‐based generalization to traditional aggregation is then proposed: ‘a‐aggregation’. It is shown that a‐aggregation cannot lead to good estimators of H, and so a new kind of aggregation, ‘d‐aggregation’, is defined, which is related to the details rather than the approximations of a multiresolution analysis. An estimator of H based on d‐aggregation has excellent statistical and computational properties, whilst preserving the spirit of aggregation. The estimator is applied to telecommunications network data.