bluuebunny/crossref_metadata_2025 huggingface dataset:
Translating the Word: Dialogism and Debate in Two Gikuyu Dictionaries
Authors: Peterson Derek
Published: March 2003

Much of the literature on missionaries and translation in colonial Africa has tended to view missionary or colonial authored texts (Bibles, dictionaries, and grammars in particular) as instruments through which foreign ways of thinking were imposed upon unsuspecting Africans. In a detailed comparison of two Gikuyu dictionaries—one authored by an Anglican missionary and the other by a Presbyterian missionary some ten years later—this article locates signiﬁcant contradictions in meanings, particularly in words associated with religion and authority. By situating these contradictions within the social history of early twentieth‐century Gikuyuland, the author is able to demonstrate that these contradictions are not “mistakes”; rather, such inconsistencies evidence the complex ontological and political debates provoked out of early evangelistic activity. For the author, who draws theoretical insight from Homi Bhabha and M. M. Bakhtin, mission texts like dictionaries are fundamentally dialogical, the product of sustained and contentious conversations between missionaries and African interlocutors. Thus, they not only shaped Gikuyu life, as earlier scholarship contended, but were profoundly shaped bycontemporary Gikuyu debates over religion, power, and authority.
“And the Bones Come Together”: Women’sReligious Expectations in Southern Africa, c. 1900–1945
Authors: Moss Barbara A.
Published: March 2003

African religious beliefs invaded Christian missions and provided the backdrop for interaction between African converts and women missionaries. African women came to missions not as tabulae rasae; their culture had stamped them with expectations and insights with which they imbibed and moulded the Christian message. They viewed religion as a resource. Their cultural expectations reinforced missionary promises and facilitated Christian conversion. As religious specialists women gained status, respect, social and economic security in pre‐colonial society because they provided necessary and important services. These expectations lingered among African women at the missions. Thus, within patriarchal Christian denominations African women often exhibited an assertiveness which missionaries misunderstood and maligned. Mission conﬂicts were based on missionary attempts to make African women dependent upon their Christian spouses. This role was contradictory to African beliefs and Christian African needs. Differences were further exacerbated by gender discrimination within the church, which affected both European and African women, and colonialism, which provided the background for Christian occupation of the colony. Although familial obligations and cultural expectations were points of contention, motherhood, literacy, and leadership training provided meeting points of mutual concern for African women and missionaries.
Fighting for the Afterlife: Spiritists, Catholics, and Popular Religion in Nineteenth‐Century France
Authors: Sharp Lynn L.
Published: March 2003

This article examines the position of nineteenth‐century French spiritism in relation to the Catholic Church. Spiritism offered an alternative “religion” to French Catholics dissatisﬁed with the church’s traditionalism in a modernizing world. I begin by describing the spiritists’ position on Catholic dogma and the movement’s place as an urban popular religion. Spiritist critiques of heaven and hell incorporated liberal and republican values, thus making it appealing to these groups who were often hostile to the church. I move next to conﬂicts between the adversaries. Spiritists, unfettered by dogma or even logic in some cases, freely incorporated the supernatural into the nineteenth‐century acceptance of Enlightenment values such as reason and science. The church, unable to deny the reality of supernatural phenomena claimed by the spiritists, limited itself to asserting the devil’s hand in these phenomena. It thus could not fully address the challenge of spiritism. Spiritism as a popular religion complicates the assumption by many folklorists regarding the disappearance of popular beliefs in the face of the modern. The article concludes with a call to modify these theories in order to understand an evolving, often urban, popular culture which integrated “tradition” and “modernity” and continually created new forms of the marvellous.
Denominational Difference in Quaker Relief Work During the Spanish Civil War: The Operation of Corporate Concern and Liberal Theologies
Authors: Mendlesohn Farah
Published: March 2003

The denominational differences between American and British relief workers in the Spanish Civil War are not immediately obvious, and cannot be identified by simple reference to the ideologies of the societies with which they claimed allegiance. This is both because orthodox American Quakerism and the theology of the London Yearly Meeting were very similar in the first half of the twentieth century, and because, when we attempt to compare the two groups, we are not comparing like with like. Those who worked for the (British) Friends Service Council (FSC) – and they came from a number of countries – were representing the witness of the London Society of Friends. Those who worked for the American Friends Service Committee (AFSC) were representing only the theology of that committee.

In the 1920s the denominational identities of the American Quakers were beginning to settle into patterns which we recognize in the twentieth century. As part of this settlement American Quakers tentatively agreed to cooperate in matters of relief, a cooperation which produced the AFSC. However, in order to walk the precarious tightrope of interdenominational tension, the AFSC was forced to develop its own independent identity and its own distinctive character. While the AFSC is not a denomination in the usual sense of the word, it is possible to see it as possessing its own culture and theologies. It has a cohesiveness that allows us to compare practice and belief with that of the FSC where it is not possible to make a comparison between American and British workers in this context – in part, because very few of the “British” in Spain were actually British – nor to compare the British and American Societies. This paper will attempt, through focusing on the place of the Peace Testimony in the relief work in which the two sets of Friends were engaged, to indicate the differences of theology and practice displayed by the two “denominations.” However, this paper should be recognized as part of a larger and longer work engaged in considering the role played by the Testimony of Social Justice in the working out of the Quaker Peace Witness in the middle years of the twentieth century.
Dietrich Bonhoeffer’s Prioritization of Church Unity (Oekumene)
Authors: Moses John A.
Published: March 2003

When Dietrich Bonhoeffer, following Karl Barth, broke with the “liberal school” of German Protestant theology, led by the famous Adolf von Harnack, he discovered that the Ecumenical Movement could be an agency for bringing about world peace, and he argued energetically for this in the various forums of the then ecumenical movement. However, to only partial avail. With the Nazi seizure of power in Germany, the urgency for the ecumenical movement to declare solidarity with the Confessing Church in Germany became acute. This was because the Nazi‐supported Reich Church and the so‐called German Christians were trying to align Christianity with Nazi ideology. Bonhoeffer proclaimed forcefully that the latter group were acting in the service of the Antichrist, driven by entirely worldly ambitions. He argued that this situation made it doubly incumbent on the churches associated in the ecumenical movement to support the Confessing Church. Indeed, he made such a declaration of solidarity the touchstone of the credibility of the ecumenical movement.

This paper seeks to trace the course of Bonhoeffer’s campaign, for which he only had the limited support of men such as Bishop Bell of Chichester. But he failed not only to persuade the Ecumenical Movement; he was also unable to convince the majority of the Confessing Church to declare unequivocally for peace against the Nazi leadership. The article concludes with the observation that the present‐day ecumenical movement has remembered Bonhoeffer’s original plea for an Ecumenical Peace Council, and that it now recognizes that Bonhoeffer confronted the Churches with a challenge that will remain on its agenda for the foreseeable future.
Are Structured Abstracts Easier to Read Than Traditional Ones?
Authors: Hartley James , Sydes Matthew
Published: March 2003

Background: Structured abstracts (which contain sub‐headings such as this one) have replaced traditional abstracts in most current medical journals. Evaluation studies have shown that such abstracts usually contain more information, are of a higher quality, and facilitate peer review.

Aim: The aim of the studies reported here was to investigate an additional, but as yet unexamined, feature of structured abstracts – namely whether or not they might be easier to read.

Method: Eight studies were carried out. The first two compared the Flesch and the Gunning readability scores of traditional abstracts that were published in particular journals with those of structured ones that were published in the same journals after these journals had moved to using structured abstracts. The next two examined the Flesch and the Gunning readability scores of traditional and structured abstracts when they were written by the same authors. The next two examined the ability of readers to re‐construct scrambled versions of abstracts to see if it was easier to re‐construct structured abstracts than it was to re‐construct traditional ones. The last two examined readers’ judgements of the readability of pairs of traditional and structured abstracts.

Results: The first two studies showed that there were no significant differences in the readability scores of the earlier and the later abstracts. The next two studies showed, however, that when authors revised traditional abstracts to produce structured versions then the structured abstracts had higher readability scores. The next two studies showed that when readers were asked to re‐sequence sentences taken from traditional and structured abstracts, they sometimes found this harder to do with traditional abstracts. The last two studies showed that readers rated structured abstracts more readable than traditional ones.

Conclusions: These studies suggest that structured abstracts may be easier to read than traditional ones – sometimes!
Social and cognitive factors influencing the reading comprehension of Arab students learning Hebrew as a second language in Israel
Authors: Abu‐Rabia Salim
Published: March 2003

This study investigated the relationship of the attitudes and cultural background of Arab students in Israel to their reading comprehension of stories from Jewish and Arab culture. Participants were 74 eighth‐grade Arab students (age 14–15 years) from Israel, learning Hebrew as a second language (L2). An attitude questionnaire, stories from Arab and Jewish culture and multiple‐choice questions about each story were used. Results indicated that students scored higher on tasks of reading comprehension with texts from their own cultural setting than with texts from a culturally unfamiliar setting. Furthermore, results of the attitude questionnaire showed that motivation of Arab students to learning Hebrew was primarily instrumental rather than integrative. A conclusion of this study is that problematic social contexts negatively affect L2 learning of minority students. In order to facilitate Hebrew L2 learning, L2 curricula should include Hebrew language texts with content culturally familiar and relevant to the life of Arab learners.
The Sources of Error in Spanish Writing (Research Note)
Authors: Justicia Fernando , Defior Sylvia , Pelegrina Santiago , Martos Francisco J.
Published: March 2003

The main aim of this study was to determine the pattern of errors in Spanish spelling. Specifically, we were interested in discovering if all Spanish words have similar levels of spelling difficulty or whether there are types of words that cause a high percentage of spelling errors. 972 children aged between 8 to 10 years were requested to write a short spontaneous story. Our objective was to analyse and to propose a classification system for the errors made by children in the initial stages of the acquisition of spelling skills. The results indicate (a) that the diverse forms of only 20 Spanish words produce 36 per cent of the spelling errors in Spanish, and (b) that substitution is the most frequent type of error (68 per cent of total errors), which occurs as a consequence of an inadequate knowledge of the rules of phoneme‐grapheme correspondence. These findings have relevance for the teaching of writing in Spanish.
Phonological recoding deficit in working memory of dyslexic teenagers
Authors: Palmer Sue
Published: March 2003

The picture span performance of developmental dyslexic teenagers (mean age 14 years 1 month) was compared to the picture span performance of both RA (mean age 9 years 0 month) and chronological age match controls (mean age 14 years 1 month). Three stimulus lists were manipulated for visual and phonological similarity. Findings indicated that all three groups showed a significant phonological similarity effect but only the dyslexic group showed a significant visual similarity effect. The presence of dual visual‐verbal coding is postulated to be responsible for the ‘noisy’ encoding which others (e.g. Johnston and Anderson, 1998; Swan and Goswami, 1997) have suggested is a root cause of dyslexia. The results are discussed in terms of developmental deficits in the central executive of the working memory system.
Predictors of Reading Recovery book levels
Authors: Hatcher Peter
Published: March 2003

The purpose of this paper is to determine whether predictor variables, selected from readability research and from teacher nomination, might be used to grade children’s early reading books. Two hundred Reading Recovery books were rated on five variables thought to represent ‘semantic’, ‘syntactic’ and ‘phonic’ features of text. The variables accounted for 83% of book level variance. In a cross‐validation exercise they were found to be stable and reliable. It is suggested that the data support the validity of the Reading Recovery book levels, and that the formula can be used by teachers to grade children’s early reading books.
The effects of reading speed and reading patterns on the understanding of text read from screen
Authors: Dyson Mary , Haselgrove Mark
Published: March 2003

With increasing use of the World Wide Web, rapid scanning or skimming of material on screen has become a frequent activity. However, the outcome of this method of reading has not been thoroughly investigated. Using a range of question types, comprehension was measured after reading from screen at both a normal and fast reading speed. In addition, by automatically recording how readers scrolled through each document, reading patterns were explored. A speed‐accuracy trade‐off was found and, in general, the recall of specific details was less accurate than responses to ‘higher order’ questions. However, questions that addressed the structure of the text were hardest. Analysis of the scrolling movements showed that the overall time spent pausing between movements was the best predictor of comprehension. At a normal reading speed, the most effective readers, in terms of higher comprehension scores, were those who spent more time between scrolling movements, which were fast and frequent.
Screen design for children’s reading: some key issues
Authors: Walker Sue , Reynolds Linda
Published: March 2003

This paper draws attention to design issues that are likely to affect the way that children interact with screen‐based information texts. It is based on the findings of the Interactive Multimedia in Primary Schools (IMPS) project funded by the British Library, carried out at The University of Reading. The paper summarises the design‐related aspects of the project, highlighting those issues that relate to access, navigation and typography. It draws together observations from teachers and children based on tape‐recorded interviews and video recordings, and research from the fields of human computer interaction, information design and education.
Testing reading comprehension of theoretical discourse with cloze
Authors: Greene Benjamin
Published: March 2003

The ability of cloze tests containing frequent, every n‐th word deletions to measure comprehension of macropropositions has been challenged on both theoretical and empirical grounds, calling into question the validity of such tests for assessing comprehension of much of the discourse encountered by university‐level students. To evaluate the comprehension of a writer’s reasoning, it is recommended that cloze tests position gaps so as to target recognition of cohesive devices and the ability to draw inferences from other sentences. To test the validity of such a design, a large sample of scores on discourse cloze tests administered in introductory college economics is compared to scores on true–false comprehension tests designed to target recognition of connective propositions. The two distributions of scores do not differ significantly in terms of mean value, dispersion or frequency distribution, suggesting that appropriately designed cloze tests can provide a valid assessment of the reader’s integration of theoretical text. In addition, the usefulness of readability formulas based on surface characteristics of text is challenged when readability is defined in terms of the difficulty of constructing a coherent representation of theoretical text.
Parents’ self‐efficacy beliefs, parents’ gender, children’s reader self‐perceptions, reading achievement and gender
Authors: Lynch Jacqueline
Published: March 2003

This study investigated the relationships among parents’ self‐efficacy beliefs, parents’ gender, children’s reader self‐perceptions, reading achievement and gender. This study consisted of 66 students, aged eight and nine, and 92 parents involved in a family literacy project for approximately one year. The study was conducted in a rural area of Eastern Canada. There were three instruments used in this study: a Questionnaire for Parents, a Reader Self‐Perception Scale (RSPS) (Henk & Melnick, 1995), and a standardised reading test (Test of Early Reading Ability‐2 – TERA‐2) (Reid, Hresko & Hammill, 1989). The Pearson‐Product‐Moment method and t‐tests were used to determine relationships in the data and to identify significant differences in scores on the instruments. Significant positive and negative relationships were found between mothers’ and fathers’ self‐efficacy beliefs and children’s reader self‐perceptions. Children’s self‐perceptions as readers significantly related to their reading achievement. Mothers had stronger beliefs than did fathers in their ability to help improve boys’ reading achievement. Significant differences favouring females were found in children’s reader self‐perceptions and their reading achievement. The findings of this study provide a basis for understanding factors related to young children’s reading achievement.
Phonological awareness in monolingual and bilingual English and Greek five‐year‐olds
Authors: Loizou Maria , Stuart Morag
Published: March 2003

This study examined and compared levels of phonological awareness in monolingual and bilingual English and Greek five‐year‐olds. Sixty‐eight children from Britain and Cyprus, matched on the basis of age, gender, non‐verbal and verbal IQ, were assigned to four groups: two bilingual (English‐Greek, Greek‐English) and two monolingual (English, Greek). Performance of the four groups on a set of six phonological tasks was compared. Bilingual children were given both English and Greek versions of the tasks; monolingual children were given the phonological tasks in their mother tongue only. Given the results of previous research, it was predicted that bilingual children would show higher levels of phonological awareness than monolingual. The children tested in Britain were already being taught to read in school, whereas those tested in Cyprus were not. On the basis of previous research, it was further predicted that there would also be effects of learning to read in an alphabetic language, such that the bilingual children tested in Britain would show higher levels of phonological awareness at the level of the phoneme than their counterparts tested in Cyprus.

Results showed that the bilingual English‐Greek children significantly outperformed the monolingual English children, but this pattern was not replicated in the bilingual Greek‐English/monolingual Greek comparisons. This difference is discussed in terms of the bilingual enhancement effect, which, according to the present data, seems to occur only when bilingual children are exposed to a second language that is phonologically simpler than their first language. Results also showed that English‐Greek bilingual children performed significantly better than Greek‐English bilinguals, especially on tasks requiring phoneme awareness. This accords well with suggestions that learning to read in an alphabetic language promotes this level of phonological awareness.
The developmental progression of comprehension‐related skills in children learning EAL
Authors: Hutchinson Jane M. , Whiteley Helen E. , Smith Chris D. , Connors Liz
Published: March 2003

Many children who speak English as an additional language (EAL) underachieve in areas of English literacy, especially in the primary years. These difficulties are often attributed to low levels of English language fluency as they enter the education system. In an effort to provide a greater understanding of this underachievement, the cognitive‐linguistic factors underlying literacy development in monolingual children and children learning EAL were examined in a three‐year longitudinal project. The project, conducted in schools in the north of England, followed the developmental progression of forty‐three children learning EAL and forty‐three monolingual children from school years Two to Four. Children were assessed on measures of reading accuracy, reading and listening comprehension, receptive and expressive vocabulary, and reception of grammar. Analysis revealed similarities between the two groups of children on reading accuracy, but children learning EAL had lower levels of vocabulary and comprehension at each point in time. Data are discussed in terms of the development of underlying language skills and the impact of these skills on both reading and listening comprehension. The implications of the findings for classroom practice are considered.
Some Methods for Investigating Spatial Clustering, with Epidemiological Applications
Authors: Anderson N. H. , Titterington D. M.
Published: March 2003

The paper considers the problem of identifying spatial clustering, for instance of one group of individuals in relation to the spatial distribution of another. First, some of the literature is reviewed, some operational problems of practical investigations are discussed and a data set is introduced that involves a group of laryngeal cancer patients and a group of lung cancer patients in south Lancashire. Two techniques, an integrated squared difference statistic and a two-dimensional version of the scan statistic, are then outlined, some of their properties are discussed and they are applied to the data set. The final section takes stock of the data analysis and the characteristics of the techniques.
Surgical Audit: Statistical Lessons from Nightingale and Codman
Authors: Spiegelhalter David J.
Published: March 2003

There is a long history of interest in examining and comparing surgical outcomes. The ‘epidemiological’ approach was initiated by Florence Nightingale in her suggestion for uniform surgical statistics, and she clearly predicted the problems that are associated with collecting, analysing and interpreting such data. Unfortunately those responsible for implementing and reporting her scheme appeared not to have shared her insight. The contrasting ‘clinical’ approach was championed by Ernest Codman in his search for full and honest appraisals of surgical errors. Once again, despite initial enthusiasm, others had great difficulty in following his example, although we discuss a recent instance of a reflective analysis of an individual surgeon’s performance. We conclude by suggesting that a synthesis between these approaches is appropriate, but we follow others in warning of the inevitable extra-statistical difficulties that will arise.
Symmetric Pattern Models: A Latent Variable Approach to Item Non-Response in Attitude Scales
Authors: O’Muircheartaigh Colm , Moustaki I.
Published: March 2003

This paper proposes a new approach to the treatment of item non-response in attitude scales. It combines the ideas of latent variable identification with the issues of non-response adjustment in sample surveys. The latent variable approach allows missing values to be included in the analysis and, equally importantly, allows information about attitude to be inferred from non-response. We present a symmetric pattern methodology for handling item non-response in attitude scales. The methodology is symmetric in that all the variables are given equivalent status in the analysis (none is designated a ‘dependent’ variable) and is pattern based in that the pattern of responses and non-responses across individuals is a key element in the analysis. Our approach to the problem is through a latent variable model with two latent dimensions: one to summarize response propensity and the other to summarize attitude, ability or belief. The methodology presented here can handle binary, metric and mixed (binary and metric) manifest items with missing values. Examples using both artificial data sets and two real data sets are used to illustrate the mechanism and the advantages of the methodology proposed.
Weighting for Item Non-Response in Attitude Scales by Using Latent Variable Models with Covariates
Authors: Moustaki Irini , Knott Martin
Published: March 2003

We discuss the use of latent variable models with observed covariates for computing response propensities for sample respondents. A response propensity score is often used to weight item and unit responders to account for item and unit non-response and to obtain adjusted means and proportions. In the context of attitude scaling, we discuss computing response propensity scores by using latent variable models for binary or nominal polytomous manifest items with covariates. Our models allow the response propensity scores to be found for several different items without refitting. They allow any pattern of missing responses for the items. If one prefers, it is possible to estimate population proportions directly from the latent variable models, so avoiding the use of propensity scores. Artificial data sets and a real data set extracted from the 1996 British Social Attitudes Survey are used to compare the various methods proposed.
Monitoring Point Patterns for the Development of Space–Time Clusters
Authors: Rogerson Peter A.
Published: March 2003

Existing statistical methods for the detection of space–time clusters of point events are retrospective, in that they are used to ascertain whether space–time clustering exists among a fixed number of past events. In contrast, prospective methods treat a series of observations sequentially, with the aim of detecting quickly any changes that occur in the series. In this paper, cumulative sum methods of monitoring are adapted for use with Knox’s space–time statistic. The result is a procedure for the rapid detection of any emergent space–time interactions for a set of sequentially monitored point events. The approach relies on a ‘local’ Knox statistic that is useful in retrospective analyses to detect when and where space–time interaction occurs. The distribution of the local Knox statistic under the null hypothesis of no space–time interaction is derived. The retrospective local statistic and the prospective cumulative sum monitoring method are illustrated by using previously published data on Burkitt’s lymphoma in Uganda.
Is Comprehensive Education Really Free?: A Case-Study of the Effects of Secondary School Admissions Policies on House Prices in One Local Area
Authors: Leech Dennis , Campos Erick
Published: March 2003

The paper reports on a study that tests the anecdotal hypothesis that parents are willing to pay a premium to secure places for their children in popular and oversubscribed comprehensive schools. Since many local education authorities use admissions policies that are based on catchment areas and places in popular schools are very difficult to obtain from outside these areas—but very easy from within them—parents have an incentive to move house for the sake of their children's education. This would be expected to be reflected in house prices. The study uses a cross-sectional sample based on two popular schools in one local education authority area, Coventry. Differences in quality of housing are dealt with by using the technique of hedonic regression and differences in location by sample selection within a block sample design. The sample was chosen from a limited number of locations spanning different catchment areas to reduce both observable and unobservable variability in nuisance effects while maximizing the variation in catchment areas. The results suggest that there are strong school catchment area effects. For one of the two popular schools we find a 20% premium and for the other a 16% premium on house prices ceteris paribus.
Predicting Multivariate Responses in Multiple Linear Regression
Authors: Breiman Leo , Friedman Jerome H.
Published: March 2003

We look at the problem of predicting several response variables from the same set of explanatory variables. The question is how to take advantage of correlations between the response variables to improve predictive accuracy compared with the usual procedure of doing individual regressions of each response variable on the common set of predictor variables. A new procedure is introduced called the curds and whey method. Its use can substantially reduce prediction errors when there are correlations between responses while maintaining accuracy even if the responses are uncorrelated. In extensive simulations, the new procedure is compared with several previously proposed methods for predicting multiple responses (including partial least squares) and exhibits superior accuracy. One version can be easily implemented in the context of standard statistical packages.
Inference for Non-random Samples
Authors: Copas J. B. , Li H. G.
Published: March 2003

Observational data are often analysed as if they had resulted from a controlled study, and yet the tacit assumption of randomness can be crucial for the validity of inference. We take some simple statistical models and supplement them by adding a parameter θ which reflects the degree of non-randomness in the sample. For a randomized study θ is known to be 0. We examine the profile log-likelihood for θ and the sensitivity of inference to small non-zero values of θ. Particular models cover the analysis of survey data with item non-response, the paired comparison t-test and two group comparisons using observational data with covariates. Some practical examples are discussed. Allowing for sampling bias increases the uncertainty of estimation and weakens the significance of treatment effects, sometimes substantially so.
Maximum Likelihood Estimation of Logistic Regression Parameters under Two-phase, Outcome-dependent Sampling
Authors: Breslow Norman E. , Holubkov Richard
Published: March 2003

Outcome-dependent sampling increases the efficiency of studies of rare outcomes, examples being case—control studies in epidemiology and choice–based sampling in econometrics. Two-phase or double sampling is a standard technique for drawing efficient stratified samples. We develop maximum likelihood estimation of logistic regression coefficients for a hybrid two-phase, outcome–dependent sampling design. An algorithm is given for determining the estimates by repeated fitting of ordinary logistic regression models. Simulation results demonstrate the efficiency loss associated with alternative pseudolikelihood and weighted likelihood methods for certain data configurations. These results provide an efficient solution to the measurement error problem with validation sampling based on a discrete surrogate.
A Second-order Adjustment to the Profile Likelihood in the Case of a Multidimensional Parameter of Interest
Authors: Stern Steven E.
Published: March 2003

Inference in the presence of nuisance parameters is often carried out by using the χ2-approximation to the profile likelihood ratio statistic. However, in small samples, the accuracy of such procedures may be poor, in part because the profile likelihood does not behave as a true likelihood, in particular having a profile score bias and information bias which do not vanish. To account better for nuisance parameters, various researchers have suggested that inference be based on an additively adjusted version of the profile likelihood function. Each of these adjustments to the profile likelihood generally has the effect of reducing the bias of the associated profile score statistic. However, these adjustments are not applicable outside the specific parametric framework for which they were developed. In particular, it is often difficult or even impossible to apply them where the parameter about which inference is desired is multidimensional. In this paper, we propose a new adjustment function which leads to an adjusted profile likelihood having reduced score and information biases and is readily applicable to a general parametric framework, including the case of vector-valued parameters of interest. Examples are given to examine the performance of the new adjusted profile likelihood in small samples, and also to compare its performance with other adjusted profile likelihoods.
Optimal Scaling of Discrete Approximations to Langevin Diffusions
Authors: Roberts Gareth O. , Rosenthal Jeffrey S.
Published: March 2003

We consider the optimal scaling problem for proposal distributions in Hastings-Metropolis algorithms derived from Langevin diffusions. We prove an asymptotic diffusion limit theorem and show that the relative efficiency of the algorithm can be characterized by its overall acceptance rate, independently of the target distribution. The asymptotically optimal acceptance rate is 0.574. We show that, as a function of dimension n, the complexity of the algorithm is O(n1/3), which compares favourably with the O(n) complexity of random walk Metropolis algorithms. We illustrate this comparison with some example simulations.
Conformal Normal Curvature and Assessment of Local Influence
Authors: Poon Wai-Yin , Poon Yat Sun
Published: March 2003

In 1986, R. D. Cook proposed differential geometry to assess local influence of minor perturbations of statistical models. We construct a conformally invariant curvature, the conformal normal curvature, for the same purpose. This curvature provides a measure of local influence ranging from 0 to 1, with objective bench-marks to judge largeness. We study various approaches to using the conformal normal curvature and the relationships between these approaches.
Bayesian Analysis of Agricultural Field Experiments
Authors: Besag Julian , Higdon David
Published: March 2003

The paper describes Bayesian analysis for agricultural field experiments, a topic that has received very little previous attention, despite a vast frequentist literature. Adoption of the Bayesian paradigm simplifies the interpretation of the results, especially in ranking and selection. Also, complex formulations can be analysed with comparative ease, by using Markov chain Monte Carlo methods. A key ingredient in the approach is the need for spatial representations of the unobserved fertility patterns. This is discussed in detail. Problems caused by outliers and by jumps in fertility are tackled via hierarchical t formulations that may find use in other contexts. The paper includes three analyses of variety trials for yield and one example involving binary data; none is entirely straightforward. Some comparisons with frequentist analyses are made.
Time Series Analysis of Non-Gaussian Observations Based on State Space Models from Both Classical and Bayesian Perspectives
Authors: Durbin J. , Koopman S. J.
Published: March 2003

The analysis of non-Gaussian time series by using state space models is considered from both classical and Bayesian perspectives. The treatment in both cases is based on simulation using importance sampling and antithetic variables; Markov chain Monte Carlo methods are not employed. Non-Gaussian disturbances for the state equation as well as for the observation equation are considered. Methods for estimating conditional and posterior means of functions of the state vector given the observations, and the mean-square errors of their estimates, are developed. These methods are extended to cover the estimation of conditional and posterior densities and distribution functions. The choice of importance sampling densities and antithetic variables is discussed. The techniques work well in practice and are computationally efficient. Their use is illustrated by applying them to a univariate discrete time series, a series with outliers and a volatility series.
Wavelet Processes and Adaptive Estimation of the Evolutionary Wavelet Spectrum
Authors: Nason Guy P. , Von Sachs R. , Kroisandt Gerald
Published: March 2003

This paper defines and studies a new class of non-stationary random processes constructed from discrete non-decimated wavelets which generalizes the Cramér (Fourier) representation of stationary time series. We define an evolutionary wavelet spectrum (EWS) which quantifies how process power varies locally over time and scale. We show how the EWS may be rigorously estimated by a smoothed wavelet periodogram and how both these quantities may be inverted to provide an estimable time-localized autocovariance. We illustrate our theory with a pedagogical example based on discrete non-decimated Haar wavelets and also a real medical time series example.
Two-step Estimation of Functional Linear Models with Applications to Longitudinal Data
Authors: Fan Jianqing , Zhang Jin-Ting
Published: March 2003

Functional linear models are useful in longitudinal data analysis. They include many classical and recently proposed statistical models for longitudinal data and other functional data. Recently, smoothing spline and kernel methods have been proposed for estimating their coefficient functions nonparametrically but these methods are either intensive in computation or inefficient in performance. To overcome these drawbacks, in this paper, a simple and powerful two-step alternative is proposed. In particular, the implementation of the proposed approach via local polynomial smoothing is discussed. Methods for estimating standard deviations of estimated coefficient functions are also proposed. Some asymptotic results for the local polynomial estimators are established. Two longitudinal data sets, one of which involves time-dependent covariates, are used to demonstrate the approach proposed. Simulation studies show that our two-step approach improves the kernel method proposed by Hoover and co-workers in several aspects such as accuracy, computational time and visual appeal of the estimators.
Expected Estimating Equations to Accommodate Covariate Measurement Error
Authors: Wang C.-Y. , Sullivan Pepe Margaret
Published: March 2003

Estimating equations which are not necessarily likelihood-based score equations are becoming increasingly popular for estimating regression model parameters. This paper is concerned with estimation based on general estimating equations when true covariate data are missing for all the study subjects, but surrogate or mismeasured covariates are available instead. The method is motivated by the covariate measurement error problem in marginal or partly conditional regression of longitudinal data. We propose to base estimation on the expectation of the complete data estimating equation conditioned on available data. The regression parameters and other nuisance parameters are estimated simultaneously by solving the resulting estimating equations. The expected estimating equation (EEE) estimator is equal to the maximum likelihood estimator if the complete data scores are likelihood scores and conditioning is with respect to all the available data. A pseudo-EEE estimator, which requires less computation, is also investigated. Asymptotic distribution theory is derived. Small sample simulations are conducted when the error process is an order 1 autoregressive model. Regression calibration is extended to this setting and compared with the EEE approach. We demonstrate the methods on data from a longitudinal study of the relationship between childhood growth and adult obesity.
Local Influence for Incomplete Data Models
Authors: Zhu Hong-Tu , Lee Sik-Yum
Published: March 2003

This paper proposes a method to assess the local influence in a minor perturbation of a statistical model with incomplete data. The idea is to utilize Cook's approach to the conditional expectation of the complete-data log-likelihood function in the EM algorithm. It is shown that the method proposed produces analytic results that are very similar to those obtained from a classical local influence approach based on the observed data likelihood function and has the potential to assess a variety of complicated models that cannot be handled by existing methods. An application to the generalized linear mixed model is investigated. Some illustrative artificial and real examples are presented.
Estimating the Number of Clusters in a Data Set Via the Gap Statistic
Authors: Tibshirani Robert , Walther Guenther , Hastie Trevor
Published: March 2003

We propose a method (the ‘gap statistic’) for estimating the number of clusters (groups) in a set of data. The technique uses the output of any clustering algorithm (e.g. K-means or hierarchical), comparing the change in within-cluster dispersion with that expected under an appropriate reference null distribution. Some theory is developed for the proposal and a simulation study shows that the gap statistic usually outperforms other methods that have been proposed in the literature.
Dynamic Models for Spatiotemporal Data
Authors: Stroud Jonathan R. , Müller Peter , Sansó Bruno
Published: March 2003

We propose a model for non-stationary spatiotemporal data. To account for spatial variability, we model the mean function at each time period as a locally weighted mixture of linear regressions. To incorporate temporal variation, we allow the regression coefficients to change through time. The model is cast in a Gaussian state space framework, which allows us to include temporal components such as trends, seasonal effects and autoregressions, and permits a fast implementation and full probabilistic inference for the parameters, interpolations and forecasts. To illustrate the model, we apply it to two large environmental data sets: tropical rainfall levels and Atlantic Ocean temperatures.
Censored Regression with the Multistate Accelerated Sojourn Times Model
Authors: Huang Yijian
Published: March 2003

Many disease processes are characterized by two or more successive health states, and it is often of interest and importance to assess state-specific covariate effects. However, with incomplete follow-up data such inference has not been satisfactorily addressed in the literature. We model the logarithm-transformed sojourn time in each state as linearly related to the covariates; however, neither the distributional form of the error term nor the dependence structure of the states needs to be specified. We propose a regression procedure to accommodate incomplete follow-up data. Asymptotic theory is presented, along with some tools for goodness-of-fit diagnostics. Simulation studies show that the proposal is reliable for practical use. We illustrate it by application to a cancer clinical trial.
Bayesian Phylogenetic Inference from Animal Mitochondrial Genome Arrangements
Authors: Larget Bret , Simon Donald L. , Kadane Joseph B.
Published: March 2003

The determination of evolutionary relationships is a fundamental problem in evolutionary biology. Genome arrangement data are potentially more informative than deoxyribonucleic acid sequence data for inferring evolutionary relationships between distantly related taxa. We describe a Bayesian framework for phylogenetic inference from mitochondrial genome arrangement data using Markov chain Monte Carlo methods. We apply the method to assess evolutionary relationships between eight animal phyla.
The Two-Way Proportional Hazards Model
Authors: Efron Bradley
Published: March 2003

Survival analysis problems often involve dual timescales, most commonly calendar date and lifetime, the latter being the elapsed time since an initiating event such as a heart transplant. In our main example attention is focused on the hazard rate of ‘death’ as a function of calendar date. Three different estimates are discussed, one each from proportional hazards analyses on the lifetime and the calendar date scales, and one from a symmetric approach called here the ‘two-way proportional hazards model’, a multiplicative hazards model going back to Lexis in the 1870s. The three are connected through a Poisson generalized linear model for the Lexis diagram. The two-way model is shown to combine the information from the two ‘one-way’ proportional hazards analyses efficiently, at the cost of more extensive parametric modelling.
Modelling Association Football Scores and Inefficiencies in the Football Betting Market
Authors: Dixon Mark J. , Coles Stuart G.
Published: March 2003

A parametric model is developed and fitted to English league and cup football data from 1992 to 1995. The model is motivated by an aim to exploit potential inefficiencies in the association football betting market, and this is examined using bookmakers’ odds from 1995 to 1996. The technique is based on a Poisson regression model but is complicated by the data structure and the dynamic nature of teams’ performances. Maximum likelihood estimates are shown to be computationally obtainable, and the model is shown to have a positive return when used as the basis of a betting strategy.
The Offender Group Reconviction Scale: A Statistical Reconviction Score for use by Probation Officers
Authors: Copas John , Marshall Peter
Published: March 2003

The criminal courts in England and Wales may request the probation service to submit pre-sentence reports which are considered by magistrates and judges before making their sentencing decision. Pre-sentence reports must include an assessment of the risk of reoffending and the risk of harm to the public which the convicted offender presents. The offender group reconviction scale is a statistical aid to such risk assessment. We describe the scale and the statistical analysis on which it is based, and we discuss some statistical aspects of its interpretation and use.