bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Consideration of Latency Periods in Cumulative Damage Models
Authors: Rittgen W. , Becker N. 
Published: May 2007

AbstractThe cumulative damage model as outlined in previous papers is unable to reproduce latency periods, particularly after short‐term exposures. A refinement being straightforward within the present frame of point process theory is proposed using displacement processes applied to the single damages. For the displacement distribution, the lognormal distribution has been suggested. As in the previous model, exact formula for the behaviour of the survival function after the onset and the cessation of an additional exposure can be derived. Qualitative examinations demonstrate that the thus extended model shows the relevant features known from reports on shortterm exposures. Fitting the model to data of follow‐up studies should provide a measure for the impact of an environmental exposure and the parameters for the distribution of the related latency period.
Choice of Smoothing Parameters for Direct Kernels in Discrimination
Authors: Tutz Gerhard 
Published: May 2007

AbstractDirect kernels, due to LAUDER (1983), as an alternative to the indirect kernel method in discriminant analysis are considered. It is shown that direct kernels may be based on any kernel function known in discrete density estimation. The choice of smoothing parameters is based on general loss functions and a family of loss functions which are specific for the discrimination problem is introduced. Examples with distance dependent and distance independent smoothing parameters are given to illustrate the applicability.
Estimation of Population Mean Under Successive Sampling Scheme when Various Weights and Regression Coefficients are Unknown
Authors: Tikkiwal G. C. , Gupta A. K. 
Published: May 2007

AbstractIn this paper properties of an estimator of the population mean on current occasion under successive sampling scheme, when various weights (φh'S) and regression coefficients (βh,h‐1) are estimated forh≥ 2, have been studied. Some empirical results on the estimation of the variance of an unbiased estimator of population mean forh= 2 are also given.
Prediction Intervals in Nonlinear Regression
Authors: Pooi A. H. 
Published: May 2007

AbstractBy treating the nonlinear model as if it were linear in the parameterization θ in the neighbourhood of the least squares estimate θ, we construct two‐sided nominally‐q‐prediction intervals by applying the usual linear model theory. The derivation of the truncated series expansion of the expected coverage of the prediction intervals at a feasible value of the parameter vector is described. The quadratic approximation of the expected coverage is then obtained for a two‐parameter nonlinear model. Finally we show how we may construct the prediction intervals when a certain type of nonlinear transformation of the parameter vector has been applied.
A Multiplicative Model Imposed More Restrictions on the Quasi‐Symmetry Model for the Analysis of Square Contingency Tables
Authors: Tomizawa Sadao 
Published: May 2007

AbstractFor the analysis of square contingency tables, this note proposes a multiplicative model imposed more restrictions on CAUSSINUS' (1965) quasi‐symmetry (QS) model. The model is not so strict as in the quasi‐double symmetry model considered by TOMIZAWA (1985b). The proposed model has the structure of the QS about the main diagonal plus an extended QS about the reverse diagonal of the square contingency table. The model is applied to the data on unaided vision of students in a university in Japan.
Confidence Intervals for the Relative Relapse Rate of Placebo VS 6‐Mercaptopurine Group of Acute Leukemia Patients Under a Random Censorship Model
Authors: Rao B. Raja , Talwalker Sheela , Kundu Debasis 
Published: May 2007

AbstractThe present paper considers a random censorhip model in which the remission times of acute leukemia patients in a study are randomly censored according to a given probability distribution and constructs confidence intervals for the Relative Relapse Rate [RRR] of the placebo versus 6‐Mercaptopurine group of acute leukemia patients. Two important models are discussed for the probability distributions of the remission times‐the exponential and the Weibull distributions. The censoring distributions are also regarded as following exponential and Weibull distributions. Several methods are used to construct the confidence intervals including its maximum likelihood estimator and its approximate sampling distribution. Sprott'S and Cox'S methods as well as the Box‐Cox transformations are also utilized.These methods are used to illustrate the construction of the confidence intervals with the FREIREICHet al. data (1964) involving a placebo and a 6‐MP group of acute leukemia patients. The results of the present paper provide valuable alternatives to the usual parametric and nonparametric tests for the treatment effect, that are discussed in the literature, such as Gehan'S test, Logrank test, and the Mantel‐Haenszel test.
Estimation of Population Regression Coefficient in Successive Sampling
Authors: Singh P. , Talwar H. K. 
Published: May 2007

AbstractAn attempt has been made to derive the theory of successive sampling for estimation of regression coefficient. The situations considered are estimation of regression coefficient for current occasion, estimation of change of regression coefficients over two occasions and estimation of average of regression coefficients over two occasions. The expressions of optimum estimators along with their variances have been worked out. On comparing their efficiencies empirically, it has been observed that similar to the estimation of mean, successive sampling can also be used with advantage for estimation of regression coefficient.
Analysis of a Series of Yield Trials with Common Checks
Authors: Singh M. 
Published: May 2007

AbstractSometimes a large number of new selected lines, although evaluated with replications, are not repeated over trials. However, there are a number of checks common across trials. The new selected lines from different trials are compared with the help of the common checks. Some limitations of an existing analysis has been described, and ways to overcome them are presented. An assessment of genotype X environment interaction has been made by check X trial interaction. A general case of incomplete block design at each trial and the connected nature of checkvstrial classification considered to obtain the adjustment for comparing selected lines from different trials. A set of cereal trials has been considered for illustration.
On Edge‐Corrected Probability Density Function Estimators for Point Processes
Authors: Doguwa S. I. , Choji D. N. 
Published: May 2007

AbstractFIKSEL(1988) provides an asymptotically unbiased kernel estimator for the densityhs(r) of the spherical contact distribution function of stationary and isotropic point processes. This paper proposes alternative estimators ofhs(r) for use with regular grid of locations. The existing estimator ofhs(r) and the alternatives proposed in this paper are then tested out in a simulation study.
Evaluating Chessboard MANOVA Designs Using Predictive and Matching Configural Frequency Analysis
Authors: Bergman L. R. , Lienert G. A. 
Published: May 2007

AbstractThis paper concerns the nonparametric evaluation of chessboard MANOVA designs. For this purpose, a matching procedure based on rook methodology is suggested as a complement to predictive coafigural frequency analysis. Using this procedure, a multivariate hypothesis can be tested in a single test. It is also possible to design a significance test to fit a specific composite hypothesis. The procedure is illustrated by results from a multivariate psychopharmacological experiment in which the effects of alcohol and caffeine were studied on test performance and volatility.
Testing Equality of Correlated Means in the Presence of Unequal Variances and Missing Values
Authors: Bhoj D. S. 
Published: May 2007

AbstractSeveral statistics are proposed for testing the hypothesis of equality of the means of bivariate normal distribution with unknown variances and correlation coefficient when observations are missing on both variatea. The null distributions of the statistics are approximated by well‐known distributions. The empirical sizes and powers of the statistics are computed and compared with paired t test and some of the known statistics based on available data. The comparisons support the use of two of the statistics proposed in this paper.
Estimation of Odds Ratios from Matched Case‐Control Studies with Incomplete Data
Authors: Haber M. , Chen C. C.‐H. 
Published: May 2007

AbstractMatched case‐control studies often include pairs with incomplete exposure information. This work presents and compares two estimators for the odds ratio that can be used when the exposures of some of the cases and controls are missing. A simulation study shows that the estimator that uses the marginal exposure frequencies is usually more efficient than the estimator based on discordant pairs.
Using Generalized Distances in Classification of Groups
Authors: Dagnelie P. , Merckx A. 
Published: May 2007

AbstractThe Mahalanobis generalized distance can advantageously be used to achieve the hierarchical clustering of groups of individuals. With a set of nearly 12,000 biometrical data, comprising populations of 14 different species of clover, we tried four methods to cluster those populations, in order to compare their results and to see whether the numerical classification obtained agrees with the botanical taxonomy. One of those methods is a conventional hierarchical clustering technique, based upon the Euclidean distances between the means of the populations, while the three other methods make use, with an increasing degree of complexity, of the generalized distances. These methods gave obviously better results.
On the Estimation of Mean Infecundable Period Following Childbirth (Using Information on Lactation Period)—A Competing Risk Theory Approach
Authors: Biswas S. , Abid M. A. 
Published: May 2007

AbstractThe methodological paper envisages to provide two measures of infecundable period following childbirth; one based on the lactation period when expiry period of amenorrhoea (P.P.A.) follows the same immediately. The other one is based on P.P.A. when expiry of P.P.A. precedes the lactation period. The weighted average of the two measures (duly weighted by the probabilities of both the events) has been given as the estimate of the mean infecundable period. A competing risk oriented approach is adopted to evolve the methodology.
Statistical Evaluation of the Effect of Gemfibrosil, a Cholesterol Reducing Drug, on Some Biochemical Coronary Heart Disease Risk Variables
Authors: Bartkowiak A. , Łsukasik S. , Chwistecki K. 
Published: May 2007

AbstractThe evaluation is based on the clinic trial with gemfibrosil (“Gevilon”, Parke‐Davis) carried out in a group of 48 patients, to whom the drug was administered in the single dose of 900 mg daily during the period of 3 months. In this paper we show the results of the treatment on five biochemical Coronary Heart Disease (CHD) risk variables: Cholesterol (CHOL), High Density Lipoprotein (HDL), Triglyccrides (TGL), Uric Acid (UA) and Glucose (GL).We are concerned with a statistical model allowing to predict which and how large changes in the considered variable can be expected in a patient taking the drug. This is done considering the “regression to the mean” effect.
A Model with Three Compartments and Nonnegative Transfers
Authors: Berg L. 
Published: May 2007

AbstractWe consider a periodic model with three compartments, which can be considered as a simplified model for the dynamics of follicles. We give necessary and sufficient conditions for the solvability in nonnegative inputs, transfers and outputs, and we determine the minimal solution. If the problem is not solvable according to measurement errors of the given data, we recover suitable values by the method of least‐squares, solving a quadratic optimization problem.
Linearized Growth Curve, Proper Age and Age at Menarche
Authors: Masuyama M. 
Published: May 2007

AbstractA mathematical model of the linearized growth curve and its physiological interpretation by the introduction of proper age, which is proportional to the chronological age, are presented here. In the second phase, but not in the first phase, this constant of proportionality is highly correlated with the age at menarche.
Some Frequentist Properties of a Bayesian Method in Clinical Trials
Authors: Ho C. H. 
Published: May 2007

AbstractInterim analysis in clinical trials involving two treatments are commonplace nowadays. Concerns from different points of view are widely seen in the literature. With a Bayesian approach there is no consideration of type I error and no power calculation. In contrast, there is no difficulty or arbitrariness in picking a prior distribution with a classical approach. In this paper, however, a stopping rule based on the Bayesian approach is discussed from a classical point of view. In specific, we consider application to normal sampling analyzed in stages and demonstrate the role of the prior distributions. In the first part of the paper, we define the stopping rules based on the posterior probabilities. We then develop the stopping boundaries in explicit forms, which can be easily computed with a hand calculator and a standard normal probability distribution table. We also summarize the frequency characteristics of this stopping rule into several results. The major question that is addressed in the second part of the paper is: how will a prior affect the results of a clinical trial study based on the posterior probabilities? The criteria for assessment will be strictly of a Neyman‐Pearson kind. We use N(v, τ2) as the prior distribution for the difference between treatments, δ. We show that the test is unbiased if v = 0 or τ = ∞. In addition, some rather obvious facts are again summarized into a couple of results. We also discuss, with a table and a figure, the power functions of non‐trivial cases with extreme v and τ using a numerical example.
Ascertainment: An Overwiew of the Classical Segregation Analysis Model for Independent Sibships
Authors: George V. T. , Elston R. C. 
Published: May 2007

AbstractSeveral different methodologies for parameter estimation under various ascertainment sampling schemes have been proposed in the past. In this article, some of the methodologies that have been proposed for independent sibships under the classical segregation analysis model are synthesized, and the general likelihoods derived for single, multiple and complete ascertainment. The issue of incorporating the sibship size distribution into the analysis is addressed, and the effect of conditioning the likelihood on the observed sibship sizes is discussed. It is shown that when the number of probands in a sibship is not specified, the corresponding likelihood can be used for a broader class of ascertainment schemes than is subsumed by the classical model.
Stratified or Multicentre Analysis with Extended Mantel–Haenszel Statistics
Authors: Schindel F. , Kwasny H. 
Published: May 2007

AbstractSince its introduction in 1959 the ability of the classical Mantel‐Haenszel (M–H) procedure for combining the odds ratios of a set of I 2 × 2 tables has led to its use also in stratified or multicentre type clinical trials. A familiar application is the M–H logrank test in survival analysis.An extension of the M–H procedure covering the case of 2 × K contingency tables (MANTEL, 1963) with ordered levels retains the essential property of pooling the results of I homogeneous tables (i.e. in absence of qualitative interactions). The assignment of some score for the K columns of a table is essential for the use of the method (in comparing 2 treatments).Some possibilities of score assignment are discussed: for clinical outcome variables such as the degree of severity of a disease, pain and so on, the score is at hand in a natural way. A less well‐known type of scoring consists in ranking the observations of a continuous variable, leading to cell sizes of 1 or 0. In this case, however, if equidistant ranking was used, the E–M–H procedure appears as an extension of Wilcoxon's rank sum test and represents a powerful non‐parametric approach in stratified or multicentre type designs with non normally distributed outcome variables.The results of some Monte‐Carlo simulations for 2 possible equidistant ranking procedures are presented, which indicate only a moderate gain in power as compared to Wilcoxon's rank sum test under the common situation of centre effects not exceeding treatment effects. Use of the E–M–H proćedure is also recommended as a simple method to overcome the potential bias due to unequally distributed prognostic factors among treatment groups.
Non‐Iterative Least Squares Estimation of Missing Values in Graeco‐Latin Square Designs
Authors: Subramant J. 
Published: May 2007

AbstractThe present paper deals with the estimation of several missing values in Graeco‐Latin Square‐designs. When the observations are missing in a particular pattern, explicit computable expressions are presented for the estimators of the missing values. This procedure is illustrated with the help of a numerical example.
Models of Chance when Measuring Interrater Agreement with Kappa
Authors: von Eye Alexander , Sörensen Silvia 
Published: May 2007

AbstractTwo measures of reliability for nominal scales are compared: Coefficient Kappa and kn, a modification suggested for agreement matrices with free marginals. It is illustrated that the evaluation of two rater's agreement may come to a contradictory conclusion, depending on whether k or kn is used. On the basis of the underlying chance models it is concluded that k and kn cannot be interpreted in the same manner. Specifically when raters disagree, the two measures can be widely discrepant.
Generalized Wilcoxon Rank Tests and Sensitivity Curves
Authors: Öhman M. L. 
Published: May 2007

AbstractIn this paper we use the sensitivity curves of TUKEY (1977) and the change of decision point (cdp) (a modified version of the breakdown point of YLVISAKER, 1977), supplemented by simulation studies to acquire knowledge about sensitivity in generalized Wilcoxon rank test statistics. Sensitivity depends on balanced or unbalanced sample size cases, censoring, combinations of failure distributions and sources of errors in the data. It is important to consider the quality of the data, and the results show that cdp and some properties of the sensitivity curves may serve as a hint when selecting a test statistic and when making a decision for a given test statistic.
Stopping Rules for Clinical Trials Implicitly Incorporating Safety Information
Authors: Ho C.‐H. 
Published: May 2007

AbstractClinical trials research is mainly conducted for the purpose of evaluating the relative efficacy of two or more treatments. However, a positive response due to treatment is not sufficient to put forward a new product because one must also demonstrate safety. In such cases, clinical trials which show a positive effect would need to accrue enough patients to also demonstrate that the new treatment is safe. It is our purpose to show how the efficacy and safety problems can be combined to yield a more practical clinical trial design. In this paper we propose an asymmetric stopping rule which allows the experimenter to terminate a clinical trial early for a sufficiently negative result and to continue to a specified number of patients otherwise. As it turns out, a few interim tests will have negligible effects on the overall significance level.
Graphical Method to Detect Departure from Normality with Special Application to Tukey's g and h Distributions
Authors: Khan B. A. , Katti S. K. 
Published: May 2007

AbstractGiven a sample, the problem of choosing one of a variety of theoretical distributions for data analysis has been a major concern to both theoretical and applied statisticians. On the basis of a graph drawn using a normal characterization, a method is given to detect departure from normality. Special mathematical study is presented for the proposed graphs. Tukey's g and h family of distributions are used as an alternate to normality.
A “Natural” Agglomerative Clustering Method for Biology
Authors: Dragomirescu L. , Postelnicu T. 
Published: May 2007

AbstractThe authors consider that cluster analysis does not objectivize but represents the biologist's subjectivity as to (1) characters considered to be significant and to (2) the way of classification. The latter, however, in authors' opinion, must be specific to the field of application. To this effect some methods are suggested for biology. The methods originate in improvements or transformation of Buser and Baroni‐Urbani's method, as well as Watanabe's method, and have the property of processing overall information with no loss or distortion. An agglomerative method which yields a necessarily unique result is suggested, being considered by the authors as a homologue of Watanabe's divisive method. The methods proposed are studied using examples logically constructed. These examples can provide from biology, especially from ecology.
Balanced Sample Generation for Predicting the Mean of a Finite Population
Authors: Bouza C. N. , Allende S. M. 
Published: May 2007

AbstractTwo algorithms for balancing samples are proposed. They permit to disminish the errors of a predictor. A simple linear regression superpopulation model generates the responses. The behavior of the predictor under two balancing algorithms is evaluated in a Montecarlo experiment. The data arose from the determination of the content of minerals and vitamins in feed.
Central Place Foraging in Nonpatchy Habitats
Authors: Botteron B. , Arditi R. 
Published: May 2007

AbstractThis paper deal with a model of optimal foraging in a habitat with arbitrary food distribution. It takes into account an arbitrary risk cost related to the distance to the animal's nest. Food acquisition and risk cost are accounted for in common units of fitness. The resulting problem is solved in the context of Calculus of Variations. The optimal duration of absence from the nest and the optimal spatial allocation of foraging time are obtained: the optimal strategy leads to separate the habitat into a region to exploit and a region to ignore. The definition of these two distinct regions depends on the relative importance of risk and food availability. With realistic risk costs, the resulting strategy indicates a highly selective behaviour when far from the nest, as observed in field studies. The model is also extended to take account of the need of returning to the nest to guard it or to feed the young.
Simultaneous Comparisons of Multiple Treatments to Two (or More) Control
Authors: Hoover D. R. 
Published: May 2007

AbstractDUNNETT (1955) developed a procedure simultaneously comparing k treatments to one control with an exact overall type I error of α when all sampling distributions are normal. Sometimes it is desirable to compare k treatments to m≧2 controls, in particular to two controls. For instance, several new therapies (e.g., pain relievers) could be compared to two standard therapies (e.g., Aspirin and Tylenol). Alternatively, a standard therapy could be very expensive, difficult to apply and/or have bad side effects, making it useful to compare each new therapy to both standard therapy and no therapy (Placebo).Dunnett's method is expanded here to give comparisons of mean values for k treatments to mean values for m≧2 controls at an exact overall type I error of α when all sampling distributions are normal. Tabled values needed to make exact simultaneous comparisons at α = .05 are given for m = 2. An application is made to an example from the literature.