Hierarchical Archimedean copula models for the analysis of binary familial data.

Archimedean copulas are commonly used in a wide range of statistical models due to their simplicity, manageable analytical expressions, rich choices of generator functions, and other workable properties. However, the exchangeable dependence structure inherent to Archimedean copulas limits its application to familial data, where the dependence among family members is often different. When response variables are binary, modeling the familial associations becomes more challenging due to the stringent constraints imposed on the dependence parameters.

Weighted scores method for regression models with dependent data.

There are copula-based statistical models in the literature for regression with dependent data such as clustered and longitudinal overdispersed counts, for which parameter estimation and inference are straightforward. For situations where the main interest is in the regression and other univariate parameters and not the dependence, we propose a "weighted scores method", which is based on weighting score functions of the univariate margins. The weight matrices are obtained initially fitting a discretized multivariate normal distribution, which admits a wide range of dependence.

What can go wrong when ignoring correlation bounds in the use of generalized estimating equations.

The analysis of repeated measure or clustered data is often complicated by the presence of correlation. Further complications arise for discrete responses, where the marginal probability-dependent Fréchet bounds impose feasibility limits on the correlation that are often more restrictive than the positive definite range. Some popular statistical methods, such as generalized estimating equations (GEE), ignore these bounds, and as such can generate erroneous estimates and lead to incorrect inferential results.

Computer modeling technology to assess extracapsular tissue coverage of whole mount sections after retropubic and laparoscopic radical prostatectomy.

Purpose: The introduction of new surgical approaches to radical prostatectomy requires methodologies that permit valid comparison that are more expedient than long-term outcomes of biochemical local and distant failure and survival. We used a computer modeling program to assess the percent of extracapsular tissue coverage of prostate glands removed by the open retropubic and laparoscopic approaches.

Materials And Methods: Specimens were available for 15 and 17 patients who underwent open and laparoscopic radical prostatectomy, respectively.