There is limited literature on the influence of smoking and BMI on success rates after intrauterine insemination (IUI). As a result of a prospective cohort study we could investigate data from 1401 IUI cycles with partner semen and 1264 IUI cycles with donor semen, primary outcome being clinical pregnancy rate (CPR). Univariate statistical analysis showed significant influence of female BMI on ...

Modeling individual heterogeneity in capture probabilities has been one of the most challenging tasks in capture-recapture studies. Heterogeneity in capture probabilities can be modeled as a function of individual covariates, but correlation structure among capture occasions should be taking into account. A proposed generalized estimating equations (GEE) and generalized linear mixed modeling (G...

The method of generalized estimating equations (GEEs) provides consistent estimates of the regression parameters in a marginal regression model for longitudinal data, even when the working correlation model is misspecified (Liang and Zeger, 1986). However, the efficiency of a GEE estimate can be seriously affected by the choice of the working correlation model. This study addresses this problem...

Marginal regression modeling with generalised estimating equations became very popular in the last decade. While the mean structure is of primary interest in rst-order generalised estimating equations (GEE1), second-order generalised estimating equations (GEE2) allow the estimation of both the mean and the association structure. It has repeatedly been shown that the usual robust variance estima...

The method of generalized estimating equations has become almost standard for analysing longitudinal and other correlated response data. However, we have found that if binary responses have less than binomial variation over clusters, and are modelled using exchangeable correlations, prevailing software implementations may give unreliable results. Bounding the negative correlation away from its ...

Clinical studies are often concerned with assessing whether different raters/methods produce similar values for measuring a quantitative variable. Use of the concordance correlation coefficient as a measure of reproducibility has gained popularity in practice since its introduction by Lin (1989, Biometrics 45, 255-268). Lin's method is applicable for studies evaluating two raters/two methods wi...

M any transportation agencies are currently involved in computerizing large quantities of gee-based data that have been traditionally relegated to filing systems. The advantages of such computerization include quicker access, more easily understood presentations that result in better interpretations, improved updating capabilities, and a more centralized and controllable source of information. ...

In toxicology, it is often of interest to perform a Dunnett’s test to determine whether a pesticide or toxic substance is different at various levels from a control. The problem is complicated by the fact that often a traditional analysis of variance (ANOVA) model cannot be used because of a complex variance structure. For example, it might be of interest to determine whether rats receiving dif...

We develop a new approach to using estimating equations to estimate marginal regression models for longitudinal data with time-dependent covariates. Our approach classifies time-dependent covariates into three types – Types I, II and III. The type of covariate determines what estimating equations can be used involving the covariate. We use the generalised method of moments to make optimal use o...

Quasi-least squares (QLS) is an alternative computational approach for estimation of the correlation parameter in the framework of generalized estimating equations (GEE). QLS allows for easier implementation of some correlation structures that are not available for GEE. We describe a user-written SAS® macro called %QLS, and demonstrate application of our macro using a clinical trial example for...