Power-Divergence Test Statistics for Testing Linear by Linear Association

Power-divergence test statistics have been considered to test linear by linear association for two-way contingency tables. These test statistics have been compared based on designed simulation study and asymptotic results for 2 × 2, 2 × 3, and 3 × 3 tables. According to the results, there are test statistics with better properties than the well-known likelihood ratio test statistic for small and moderate samples.     

Analysis of categorical data obtained by stratified random sampling

Analysis of categorical data by linear models is extended to data obtained by stratified random sampling. It is shown that, asymptotically, proportional allocation reduces the variances of estimators from those obtained hy simple random sampling. The difference between the asymptotic covariance matrices of estimated parameters obtained by simple random sampling and stratified random sampling with proportional allocation is shown to be positive definite vinder fairly non-restrictive conditions, when an asymptotically efficient method of estimation is used. Data from a major community study of mental health are used to illustrate application of the technique.     

Visualizing main effects and interaction in multiple non-symmetric correspondence analysis

Non-symmetric correspondence analysis (NSCA) is a useful technique for analysing a two-way contingency table. Frequently, the predictor variables are more than one; in this paper, we consider two categorical variables as predictor variables and one response variable. Interaction represents the joint effects of predictor variables on the response variable. When interaction is present, the interpretation of the main effects is incomplete or misleading. To separate the main effects and the interaction term, we introduce a method that, starting from the coordinates of multiple NSCA and using a two-way analysis of variance without interaction, allows a better interpretation of the impact of the predictor variable on the response variable. The proposed method has been applied on a well-known three-way contingency table proposed by Bockenholt and Bockenholt in which they cross-classify subjects by person's attitude towards abortion, number of years of education and religion. We analyse the case where the variables education and religion influence a person's attitude towards abortion.     

Time series analysis of categorical data using auto-odds ratio function

In this paper, we consider the auto-odds ratio function (AORF) as a measure of serial association for a stationary time series process of categorical data at two different time points. Numerical measures such as the autocorrelation function (ACF) have no meaningful interpretation, unless the time series data are numerical. Instead, we use the AORF as a measure of association to study the serial dependency of the categorical time series for both ordinal and nominal categories. Biswas and Song [Discrete-valued ARMA processes. Stat Probab Lett. 2009;79(17):1884–1889] provided some results on this measure for Pegram's operator-based AR(1) process with binary responses. Here, we extend this measure to more general set-ups, i.e. for AR(p) and MA(q) processes and for a general number of categories. We discuss how this method can effectively be used in parameter estimation and model selection. Following Weiß [Empirical measures of signed serial dependence in categorical time series. J Stat Comput Simul. 2011;81(4):411–429], we derive the large sample distribution of the estimator of the AORF under independent and identically distributed (iid) set-up. Some simulation results and two categorical data examples (one is ordinal and other nominal) are presented to illustrate the proposed method.     

Modelling paired categorical outcomes in clinical trials

The goal of this paper is to discuss methods for testing the homogeneity of treatment‐induced changes in trials with paired categorical responses. Widely used marginal homogeneity tests ignore the information contained in concordant pairs of observations and become highly underpowered for configurations of parameters encountered in real trials. This paper considers models for paired binary or ordinal outcomes based on both discordant and concordant pairs that provide a natural extension of marginal models. Likelihood‐ratio tests associated with these models are developed and are demonstrated to be at least as powerful as or more powerful than marginal homogeneity tests. The proposed models are easy to fit using standard statistical software. Copyright © 2003 John Wiley & Sons, Ltd.     

内涵命题和外延命题理论对解决直言命题问题的贡献

传统形式逻辑直言命题理论存在着许多的弊端。一些现行的形式逻辑读本尽管做了些改进,但是仍然没有从根本上解决问题,而且还增加了新的麻烦。内涵命题与外延命题理论是当代形式逻辑的重要特色理论之一,它在解决直言命题理论中存在的问题作出了重要贡献。深刻剖析直言命题中存在的弊病对传统形式逻辑的发展与完善有着重要的意义。     

Weighted bagging: a modification of AdaBoost from the perspective of importance sampling

We motivate the success of AdaBoost (ADA) in classification problems by appealing to an importance sampling perspective. Based on this insight, we propose the Weighted Bagging (WB) algorithm, a regularization method that naturally extends ADA to solve both classification and regression problems. WB uses a part of the available data to build models, and a separate part to modify the weights of observations. The method is used with categorical and regression tress and is compared with ADA, Boosting, Bagging, Random Forest and Support Vector Machine. We apply these methods to some real data sets and report some results of simulations. These applications and simulations show the effectiveness of WB.     

Testing stochastic orders in tails of contingency tables

Testing for the difference in the strength of bivariate association in two independent contingency tables is an important issue that finds applications in various disciplines. Currently, many of the commonly used tests are based on single-index measures of association. More specifically, one obtains single-index measurements of association from two tables and compares them based on asymptotic theory. Although they are usually easy to understand and use, often much of the information contained in the data is lost with single-index measures. Accordingly, they fail to fully capture the association in the data. To remedy this shortcoming, we introduce a new summary statistic measuring various types of association in a contingency table. Based on this new summary statistic, we propose a likelihood ratio test comparing the strength of association in two independent contingency tables. The proposed test examines the stochastic order between summary statistics. We derive its asymptotic null distribution and demonstrate that the least favorable distributions are chi-bar distributions. We numerically compare the power of the proposed test to that of the tests based on single-index measures. Finally, we provide two examples illustrating the new summary statistics and the related tests.     

Comparing diagnostic tests with missing data

When missing data occur in studies designed to compare the accuracy of diagnostic tests, a common, though naive, practice is to base the comparison of sensitivity, specificity, as well as of positive and negative predictive values on some subset of the data that fits into methods implemented in standard statistical packages. Such methods are usually valid only under the strong missing completely at random (MCAR) assumption and may generate biased and less precise estimates. We review some models that use the dependence structure of the completely observed cases to incorporate the information of the partially categorized observations into the analysis and show how they may be fitted via a two-stage hybrid process involving maximum likelihood in the first stage and weighted least squares in the second. We indicate how computational subroutines written in R may be used to fit the proposed models and illustrate the different analysis strategies with observational data collected to compare the accuracy of three distinct non-invasive diagnostic methods for endometriosis. The results indicate that even when the MCAR assumption is plausible, the naive partial analyses should be avoided.     

Latent groups and latent traits of participation in bullying via factor mixture analysis: An exploratory study

In this study, we drew on a person-centred approach to explore forms of involvement and roles in bullying. More specifically, we applied Factor Mixture Analysis (FMA) to an in-depth measure of bullying roles, with a view to identifying latent dimensions of participation in bullying and latent groups characterised by differential behavioural patterns. Participants were 899 high school students (51% females) attending the 9th (49%) and 11th grades (51%). The data analysis revealed six latent behavioural dispositions. Four of these overlapped with behavioural patterns typical of previously identified forms of participation in bullying, while two factors shed new light on bullying behaviours. We also identified four latent groups, whose profiles were only partially aligned with the roles previously theorised in the literature.