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...

In this article, we propose a generalized estimating equations (GEE) approach for correlated ordinal or nominal multinomial responses using a local odds ratios parameterization. Our motivation lies upon observing that: (i) modeling the dependence between correlated multinomial responses via the local odds ratios is meaningful both for ordinal and nominal response scales and (ii) ordinary GEE me...

When inferences focus on population averages, one can directly model all of the marginal expectations E(Yij) = μij in terms of covariates of interest. This is typically done via h(μij) = x ′ ijβ, with h(·) some known link function, such as the logit link for binary responses. The marginal variance depends on the marginal mean according to Var(Yij) = v(μij)φ, where v(·) is a known variance funct...

BACKGROUND The generalized estimating equations (GEE) technique is often used in longitudinal data modeling, where investigators are interested in population-averaged effects of covariates on responses of interest. GEE involves specifying a model relating covariates to outcomes and a plausible correlation structure between responses at different time periods. While GEE parameter estimates are c...

The National health and nutrition examination survey (NHANES) is a respected nation-wide program in charge of assessing the health and nutritional status of adults and children in United States. Recent cal research found that folic acid play an important role in preventing baby birth defects. In this paper, we use the generalized estimating equation (GEE) method to study the generalized linear ...

We examined the effect of aging and cortical stroke on rate motor adaptation (adaptation rate) amount performance gains plateau) in balance skills. Fourteen older (≥60 years) fifteen younger (<60 adults with chronic stroke, thirteen healthy participated. Participants experienced 8 consecutive gait-slips (≤45 cm) to their non-paretic/dominant limb. Slip outcome (backward/no loss) was compared...

We propose two model selection criteria relying on the bootstrap approach, denoted by QAICb1 and QAICb2, in framework of linear mixed models. Similar to justification Akaike Information Criterion (AIC), proposed QAICb2 are proved as asymptotically unbiased estimators Kullback–Leibler discrepancy between a candidate true model. However, they defined quasi-likelihood function instead likelihood p...

Many different methods have been proposed for the analysis of cluster randomized trials (CRTs) over the last 30 years. However, the evaluation of methods on overdispersed count data has been based mostly on the comparison of results using empiric data; i.e. when the true model parameters are not known. In this study, we assess via simulation the performance of five methods for the analysis of c...

The robust or sandwich estimator is common to estimate the covariance matrix of the estimated regression parameter for generalized estimating equation (GEE) method to analyze longitudinal data. However, the robust estimator would underestimate the variance under a small sample size. We propose an alternative covariance estimator to the robust estimator to improve the small-sample bias in the GE...