Tests of homogeneity in zero-inflated models for count data have been well discussed in the literature, but the existing methodologies have relied primarily on score statistics. An often cited justification for the use of these statistics is that they do not require the model to be fitted under the alternative. But the advent of computer software with robust functions and procedures has made it...

The use of longitudinal data for studying cross-time changes is built on the key assumption that properties (e.g., slopes and intercepts) of the repeatedly-used items remain unchanged over time. True changes in the latent variables are indistinguishable from item-level changes when items exhibit differential item functioning (DIF) across time points. To date, no research has extended the modifi...

We propose a test for the order of integration of the univariate components of a vector process integrated of order two, i.e. an I(2) process, given by an autoregressive model. The null hypothesis of the test is that the particular univariate time series is an I(1) process. The hypotheses are formulated as linear restrictions on the directions orthogonal to the I(1) cointegration space. The sta...

We demonstrate the equivalence between commonly used test statistics for out-of-sample forecasting performance and conventional Wald statistics. This equivalence greatly simplifies the computational burden of calculating recursive out-of-sample test statistics and their critical values. Moreover, for the case with nested models we show that the limit distribution, which has previously been expr...

The classical quadratic loss for the partially linear model (PLM) and the likelihood function for the generalized PLM are not resistant to outliers. This inspires us to propose a class of “robust-Bregman divergence (BD)” estimators of both the parametric and nonparametric components in the general partially linear model (GPLM), which allows the distribution of the response variable to be partia...

With the dramatic technological developments of genome-wide association single-nucleotide polymorphism (SNP) chips and next generation sequencing, human geneticists now have the ability to assay genetic variation at ever-rarer allele frequencies. To fully understand the impact of these rare variants on common, complex diseases, we must be able to accurately assess their statistical significance...

BACKGROUND Women have generally been found to be the victims of violence, but scant attention has been paid to the characteristics of women who perpetrate aggression and violence. In South Africa, violence is a prevalent societal issue, especially in the Western Cape. METHOD This study aimed at identifying factors that were associated with aggression among a sample of 720 substance-using wome...

Despite the successful discovery of hundreds of variants for complex human traits using genomewide association studies, the degree to which genes jointly affect disease risk is largely unknown. One obstacle toward this goal is that the computational effort required for testing gene-gene interactions is enormous. As a result, numerous computationally efficient tests were recently proposed, such ...