bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of Data Quality: Errors of Measurement and Errors of Process
Authors: Arndt Stephan , Woolson Robert W. 
Published: May 2007

AbstractAs projects progress from pilot studies with few simple variables and small samples, the research process as a whole becomes qualitatively more complex and subject to an array of contamination by errors and mistakes. Data usually undergo a series of manipulations (e.g., recording, computer entry, transmission) prior to final statistical analysis. The process, then, consists of numerous operations only ending with eventual statistical analysis and write‐up. We present a means of estimating the impact of process error in the same terms as psychometric reliability and discuss the implications for reducing the impact of errors on overall data quality.
Use of Probability Weighted Moments in the Analysis of Means
Authors: Muhammad F. , Ahmad S. , Abiodullah M. 
Published: May 2007

AbstractIn the analysis of means the estimate of σ is usually calculated using range. In this study it is proposed that the linear estimate of σ based on probability weighted moments should be used. A simulation study based on 1000 values suggested that the linear estimate of σ using probability weighted moments is more close to the original value. In the simulations different distributions such as normal, t, Cauchy and exponential were assumed.
Estimation of Exponential Parameters in the Presence of Outliers
Authors: Jeevanand E. S. , Nair N. Unnikrishnan 
Published: May 2007

AbstractIn the present paper we discuss the estimation of the parameter and survival function of an exponential population. It is assumed that the sample based on which the estimation is done, containskoutliers that are also exponentially distributed with parameter, a constant multiple of that of the original distribution.
On Presenting Results of Statistical Analyses in Scientific Journals
Authors: Finney David J. 
Published: May 2007

AbstractIn many biological and other scientific journals, a reader's understanding of a paper to the argument of which statistical methods and analyses are important is often impeded by confusions of terminology and ambiguities of symbols. This is not solely because statistics is a difficult subject for biologists! If an editor were to formulate and make known a code of statistical symbols, abbreviations, and technical terms that in his journal will be regarded as part of the normal language of science, an author could use these without need for explanation each time. Every author would remain free to depart from the code, provided that he defined clearly his own usages. Such a policy, supported by the journal's referees, would do much to remove the frequent necessity for a reader to guess an author's meaning. Similarly considerations apply to the use of statistical software packages, where there is an evident need for an author to declare what software (if any) he has used, in much the same way as, by established custom, he will carefully specify his experimental materials and methods where these in any respect differ from the obvious.The present paper is written to stimulate constructive debate, and in no way to dogmatize on the merits or faults of particular statistical methods. Its underlying spirit is that the author of a scientific communication has a duty to describe the making of his observations, the conduct of his computations, and the performance of his computations with a clarity that would permit their repetition by another scientist who has access to the appropriate facilities and resources.
Pooling Strategies for Screening Blood in Areas with Low Prevalence of HIV
Authors: Lan Shou‐Jen , Hsieh Chung‐Cheng , Yen Yea‐Yin 
Published: May 2007

AbstractHuman immunodeficiency virus (HIV) infection has serious consequences and must be kept out of blood supplies. Screening to ensure the safety of blood supplies is associated with a very high cost. The idea of pooling test samples to obtain significant savings was first suggested in 1943. Recently pooling sera has gained wider interest both as a means to determine the HIV seroprevalence rate in general populations and to weed out all HIV‐positive units in blood supplies. We describe a simple method for detecting seropositive samples in mass screening. This method determines the pooling size based on the estimated prevalence rate. Although several repooling stages are allowed, these will be kept to a minimum since the more stages that are required, the greater chance for human and technical errors. The criteria to end pooling are based on both the savings rate and the relative cost between the preparation and the actual test. Two examples illustrate the applications of this method in determining the number of samples to be pooled in successive stages and the resulting savings rate.
Consensus Principal Components
Authors: Lefkovitch L. P. 
Published: May 2007

AbstractFrom the polar forms of the principal components corresponding with each of a set of covariance (or correlation) matrices, a linear combination based on their inner products is defined as the polar form of the consensus. The corresponding eigenvectors form an orthogonal matrix which rotates each of the covariance matrices to approximate diagonal form. From the norms of the polar forms, these eigenvectors can be used to estimate a common covariance matrix. These procedures are illustrated by a numerical example.
Unbiased Estimation of Odds Ratio by Using Negative Binomial Plans
Authors: Roberts Charles Dewitt 
Published: May 2007

AbstractThe use of the negative binomial distribution in both the numerator and denominator in prospective studies leads to an unbiased estimate of the odds ratio and an exact expression for its variance. Sample sizes that minimize the variance of odds ratio estimates are specified. The variance of the odds ratio estimate is shown to be close to the Cramér‐Rao lower bound.
Testing the Equality of Dependent Variances
Authors: Modarres Reza 
Published: May 2007

AbstractThe likelihood ratio test for testing equality of vgE;2 correlated variables is developed. In general, evaluation of the test statistic involves the iterative optimization of a likelihood function with 1 + v(v – 1)/2 parameters. The explicit form of the test statistic is derived in the bivariate case, and an iterative algorithm for determining the maximum likelihood estimates is suggested. A limited Monte Carlo study determines the behavior of the proposed procedure under the null hypothesis and variety of parameter values.
Application of Partially Balanced Block Designs to Factorial Experiments
Authors: Brzeskwiniewicz Henryk 
Published: May 2007

AbstractIn this paper we present partially balanced block designs with Fp and Cp association schemes. These designs play a great role in the experimental theory since they can be applied to factorial experiments. A particular stress is put on the formulation of association schemes p and Cp, presentation of exemplary constructions of these designs and their analysis of variance. The presented considerations are abundantly illustrated with examples.
On Testing for Non‐Additivity in Factorial Experiments
Authors: Zafar‐Yab Mohammad 
Published: May 2007

AbstractIn analysis of variance the assumption of non‐additivity has more serious consequences on the interpretation of results than the assumptions of non‐normality or non‐homogeneity of variances. Tukey (1949, 1955) suggested a procedure for separating out a single degree of freedom for non‐additivity for two factor and multi‐factor experiments, respectively. In multifactor experiments Tukey's procedure does not indicate which combinations of the factors contribute to non‐additivity. In this paper a procedure is proposed which separates out a sum of squares with a single degree of freedom from each of the 2P−P−1 interactions in aP‐factor experiment.
Parameter Estimation in Systematic Sampling
Authors: Schneeberger Hans 
Published: May 2007

AbstractFirst it is shown that an estimate of the variance of the sample‐mean in systematic sampling from a non‐autocorrelated population with linear trend, which is published in textbooks, isn't a suitable estimate: It is biased and not dependent on the essential parameter, the slope of the linear trend.In section 2 an unbiased estimate of the variance is given. As estimate of the sample‐mean we take the same as usually used in literature.In section 3 a centric estimate of the sample‐mean is introduced, which takes into consideration the slope of the trendline. It is shown that this estimate is unbiased; an unbiased estimate of its variance is given.
Fecundibility and Social Development in China: Changes in the Distribution of the First Conception Interval
Authors: Sturm Roland , Zhang Junsen 
Published: May 2007

AbstractWhile it is typically assumed that the hazard of conception of a susceptible woman is either constant or decreasing, we find evidence that the hazard is increasing with the duration of marriage in China. This positive duration dependence may reflect the effects of spouses getting accustomed to each other and may exist in other “traditional” societies. We also explore whether changing customs may lead to changes in the duration dependence across cohorts or provinces. We find a small decline in the positive duration dependence over time in one province, which might be interpreted as a diminishing “late honeymoon”‐effect. Somewhat stronger is the difference between the more rural provinces Hebei and Shaanxi and the urbanized municipality of Shanghai.
Tree‐Structured Exponential Regression Modeling
Authors: Ahn Hongshik 
Published: May 2007

AbstractA method for fitting piecewise exponential regression models to censored survival data is described. Stratification is performed recursively, using a combination of statistical tests and residual analysis. The splitting criterion employed in cross‐validation is the average squared error of the residuals. The bootstrap is employed to keep the probability of a type I error (the error of discovering two or more strata when there is only one) of the method close to a predetermined value. The proposed method can thus also serve as a formal goodness‐of‐fit test for the exponential regression model. Real and simulated data are used for illustration.
Recursive Residuals for Multivariate Field Processes
Authors: Tobing H. , McGilchrist C. A. 
Published: May 2007

AbstractVector recursive residuals are developed for multivariate regression models on a field. A vector response variable is observed at points on a rectangular grid, together with regression variables measured at the same points. Neighbouring values of the response vector may be correlated and simple models are considered using a direct product structure for the variance matrix. Subsequent to obtaining vector recursive residuals principal component analysis is applied to obtain an evaluation of any changes that may be occurring in the regression relationship over the field. The method is then applied to the problem of detecting zones of bush fire damage and recovery from LANDSAT data.
Analysis of Variety Trials in the Presence of Non‐Random Time Effect
Authors: Odulaja A. , Afonja B. , Bamiduro T. A. 
Published: May 2007

AbstractThe assumption of random year effect in the analysis of variety trials data over locations and years clearly contradicts the practice of conducting the trials over only a few consecutive years. A method of analysis of such trials which assumes that the year‐dependent effects are serially correlated is proposed in this paper to cater for the non‐randomness in the selection of years of the experiments. A simple autoregressive model was assumed for the serial relationship. A reduction in the variance estimate of the difference between two variety means was obtained using this method.
Non‐Standard Log‐Linear Models for Orthogonal Prediction Configural Frequency Analysis
Authors: von Eye Alexander , Rovine Michael J. 
Published: May 2007

AbstractThe paper discusses LAUTSCH, LIENERT. and VON EYE'S (1992) orthogonal prediction configural frequency analysis (PCFA). Problems with this approach result from a lack of rules for specification of orthogonal comparisons, and because it is not obvious which comparisons are orthogonal. As an alternative it is proposed estimating non‐standard log‐linear models. These models specify orthogonal PCFA comparisons via orthogonal effect coding variables. This approach kadvantageous in that it allows researchers to simultaneously test orthogonal comparisons and PCFA parameter estimates.
Influence of the Interaction for Fitness on the Population Structure
Authors: Bartoloni Norberto 
Published: May 2007

AbstractThe incidence of non‐allelic interaction for fitness in a diallelic digenic model is analyzed. Three types of interaction between the fitnesses are considered, namely: i) additive, ii) exponential and, iii) logarithmic. The model of MATHER and JINKS (1970) is applied in the computation of the interaction parameters. The theory of finite absorbing Markov chains (FELLER, 1968) is utilized in the representation of the genotypic structure of the selfing population over time. Expressions depending on the parameters of interaction are obtained for the mean number of generations that the process of genetic information flow delays in transitions among transient states. Also, a numerical example is studied in which the mean absorption times and the variances are calculated. Finally, the impact of fitness interaction on the genetic diversity of some populations is analyzed through the calculation of the genetic information neg‐entropy (BRILLOUIN, 1959).
A Mathematical Model for the Effect of Water Pollutants on the Growth Pattern of Pollen
Authors: Pal Srimanta , Pal Ruma 
Published: May 2007

AbstractThe heavy metals as water pollutants had some adverse effects on the growth pattern of pollen grains of the aquatic macrophytes viz. Ottelia, Vallisneria, Hyderilla and Eichhornia. The germination of pollen grains were inversely proportional and the abnormality of pollen tube and the flowering time were directly proportional to the concentration of the heavy metal. In this paper we have presented a mathematical model that is the germinability and the abnormality changes with the log‐value of concentration in a straight line fashion. Also the flowering time changes with treatment time in an exponential pattern.
Some Results on the Tukey‐Mclaughlin and Yuen Methods for Trimmed Means when Distributions are Skewed
Authors: Wilcox Rand R. 
Published: May 2007

AbstractIn applied work, distributions are often highly skewed with heavy tails, and this can have disastrous consequences in terms of power when comparing groups based on means. One solution to this problem in the one‐sample case is to use the TUKEY and MCLAUGHLIN (1963) method for trimmed means, while in the two‐group case YUEN's (1974) method can be used. Published simulations indicate that they yield accurate confidence intervals when distributions are symmetric. Using a Cornish‐Fisher expansion, this paper extends these results by describing general circumstances under which methods based on trimmed means can be expected to give more accurate confidence intervals than those based on means. The results cover both symmetric and asymmetric distributions. Simulations are also used to illustrate the accuracy of confidence intervals using trimmed means versus means.
Preliminary Selection of Sires on Partial Records in Dairy Cattle
Authors: Sethi I. C. , Jain J. P. 
Published: May 2007

AbstractProgeny testing of sires is costly as well as time consuming. The cost and testing time for part sample of sires can be reduced by basing sire evaluation on partial first lactation records. But it results in genetic loss due to decrease in the accuracy of selection. The present paper is an empirical attempt to study the optimum level of preliminary culling on partial records from two different considerations for both large and small populations. It is seen that even for moderate genetic correlation between partial and complete records ( = 0.6) preliminary culling as high as 50% can be effected with advantage.
Robustness of the Standard Deviation and Other Measures of Dispersion
Authors: Högel J. , Schmid W. , Gaus W. 
Published: May 2007

AbstractContaminated observations (e.g. outliers) and heavy tails in the underlying distribution influence the standard deviation as a measure of dispersion even more than, e.g., the mean. Other measures of dispersion, namely absolute deviation, (α, β)‐trimmed standard deviation, interquartile range and median absolute deviation (MAD) are defined for population, their properties — especially robustness — are explained and estimators are given, discussed and computed for a medical example. It is investigated how these measures of dispersion can be used to estimate a scale parameter of the underlying distribution more robustly. In numerical comparisons and simulations the robustness of these measures is demonstrated for heavy tailed distributions and contaminated distributions. Among other proposals it is recommended to use the (α, β)‐trimmed standard deviation and transform it to the ordinary standard deviation for easier interpretation, if possible.
A Group Sequential Method for one Standard Control and more than one Experimental Treatment
Authors: Lui Kung‐Jong 
Published: May 2007

AbstractMany group‐sequential test procedures have been proposed to meet the ethical need for interim analyses. All of these papers, however, focus their discussion on the situation where there are only one standard control and one experimental treatment. In this paper, we consider a trial with one standard control, but with more than one experimental treatment. We have developed a group‐sequential test procedure to accommodate any finite number of experimental treatments. To facilitate the practical application of the proposed test procedure, on the basis of Monte Carlo simulation, we have derived the critical values of α‐levels equal to 0.01, 0.05 and 0.10 for the number of experimental treatments ranging from 2 to 4 and the number of multiple group sequential analysis ranging from 1 to 10. Comparing with a single non‐sequential analysis that has a reasonable power (say, 0.80), we have demonstrated that the application of the proposed test procedure may substantially reduce the required sample size without seriously sacrificing the original power.
Experiment with Split‐Plot Generated by PBIB Designs
Authors: Brzeskwiniewicz Henryk 
Published: May 2007

AbstractThe paper refers to the construction of two‐factor experiments carried out in incomplete split‐plot design in which levels of both factors occur as treatments in PBIB designs. It presents also the analysis of variance of these experiments based on partial analyses in the so called strata. These strata are connected with the variability between subplots inside wholeplots, between the wholeplots inside blocks and between blocks inside the total experiment.
Fitting Survival Data to a Piecewise Linear Hazard Rate in the Presence of Covariates
Authors: Recknor Julie C. , Gross Alan J. 
Published: May 2007

AbstractThis paper extends the work of KODLIN (1967), who proposed a method for analyzing patient survival data wherein the hazard rate was linearly related to the survival time. The present paper extends Kodlin's model to permit maximum likelihood estimation of the parameters so that covariate effects are included and the slope and intercept parameters are allowed to change over fixed intervals of the time domain of study. An illustration of the method using multiple myeloma data is given and the results are compared with those of Kodlin's model, the Feigl‐Zelen, Zippin‐Armitage model, the exponential model, and Cox's proportional hazards model.
On A Statistical Test to Detect Spatial Pattern
Authors: Sun Ping , Hughes G. 
Published: May 2007

AbstractIn the analysis of spatial patterns, the most extensively used index of dispersion is s2/m in which s2 and m are respectively the sample variance and sample mean of the count x in each sample unit. For statistical testing, the statistic I' = (n — 1) s2/m has been introduced since it has an approximate X distribution under the null hypothesis that individuals are distributed randomly. The main problem with the use of index I' is that the random distribution and the superdispersed distribution are not distinguished. In this paper, we have tried to induce a new statistical method for the detection of spatial pattern, based on the special characteristic of Poisson distribution that both of the m and s2 are the unbiased estimates of the parameter.
Inference on Collapsibility in Generalized Linear Models
Authors: Greenland S. , Maldonado George 
Published: May 2007

AbstractGREENLAND and MICKEY (1988) derived a closed‐form collapsibility test and confidence interval forIxJxKcontingency tables with qualitative factors, and presented a small simulation study of its performance. We show how their method can be extended to regression models linear in the natural parameter of a one‐parameter exponential family, in which the parameter of interest is the difference of “crude” and “adjusted” regression coefficients. A simplification of the method yields a generalization of the test for omitted covariates given by HAUSMAN (1978) for ordinary linear regression. We present an application to a study of coffee use and myocardial infarction, and a simulation study which indicates that the simplified test performs adequately in typical epidemiologic settings.
Lessons learned from building and calibrating the ICWall, a stereo tiled display
Authors: van der Schaaf Tom , Germans Desmond , E. Bal Henri , Koutek Michal 
Published: May 2007

AbstractImplementation of stereo tiled displays is a rather demanding task. In this article we want to share the lessons we have learned during the design and construction of the ICWall tiled display. This large display, used in a classroom setting, is a high‐resolution stereo tiled display (2 × 8 tiles), built from low‐cost commodity components. The overall image is produced by an array of projectors. When building such a system, a key challenge is to align the projector images. We describe our automated approach for alignment/calibration of the left‐ and right‐eye stereo images. We provide measurements that show accuracy of this procedure. We explain and compare two calibration approaches: a single‐pass and a two‐pass rendering method to align the tiled images. We explain how to provide seamless image on the tiled display and which issues have to be solved. We also discuss the depth perception issues on the ICWall for the large audiences. Another important aspect, is the architecture of the software used for PC‐cluster‐based rendering. We describe Aura, the parallel scene graph API that is used for rendering on our tiled display. Copyright © 2007 John Wiley & Sons, Ltd.