According to the authors, time-modified confounding occurs when the causal relation between a time-fixed or time-varying confounder and the treatment or outcome changes over time. A key difference between previously described time-varying confounding and the proposed time-modified confounding is that, in the former, the values of the confounding variable change over time while, in the latter, t...

Covariate adjustment using linear models for continuous outcomes in randomized trials has been shown to increase efficiency and power over the unadjusted method in estimating the marginal effect of treatment. However, for binary outcomes, investigators generally rely on the unadjusted estimate as the literature indicates that covariate-adjusted estimates based on the logistic regression models ...

Whilst estimation of the marginal (total) causal effect of a point exposure on an outcome is arguably the most common objective of experimental and observational studies in the health and social sciences, in recent years, investigators have also become increasingly interested in mediation analysis. Specifically, upon evaluating the total effect of the exposure, investigators routinely wish to m...

where u ∼ N(0, G) and 2 ∼ N(0, R) with u and 2 independent. This model can be interpreted as Y |β, u ∼ N(Xβ+Zu,R), u ∼ N(0, G), yielding (on integrating out u) the marginal model Y |β ∼ N(Xβ,ZGZ + R). Let V = ZGZ + R. Then the maximum penalized likelihood estimates of β and u given G and R are given by θ̂ = [ β̂ û ] = (CTR−1C + B)−1CTR−1y (A.2) where C = [X Z] and B is the block diagonal matrix w...

Longitudinal studies, where data are repeatedly collected on one subject over a period, are common in medical research. When effect of a time-varying exposure on an outcome of interest is measured at different time points, standard statistical methods fail to give robust estimate in the presence of time-dependent confounders. There is alternative method avoid, that is, inverse probability weigh...

A concept known as ‘marginal gains’, an approach to performance improvement in elite sport came to prominence during the London 2012 Olympics when Team GB cycling won a record eight gold medals. Since National Lottery funding was awarded in 1997 to develop British cycling, the ethos of making aggregated small gains in many areas to improve overall performance has been central to its success. Th...

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STATEMENT OF PROBLEM Monolithic zirconia crowns fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) have recently become a common practice for the restoration of posterior teeth. The marginal fit of monolithic zirconia crowns may be affected by different cement space parameters set in the CAD software. Information is scarce regarding the effect of cement space on th...

The aim of this study is to evaluate the effect of preheating on composite resins’ mechanical and physical properties. Preheating of composite resins positively affects the degree of conversion, viscosity, microleakage, marginal adaptation, microhardness and color change however, the flexural strength is adversely affected.  

according to the recent literature, the expansion of intra-industry trade increases the intra-industrial excess job reallocation. based on lovely and nelson (2002), this study examined the hypothesis that marginal intra-industry trade has a positive effect on the excess job reallocation in iranian industries. therefore, we have employed a panel technique for iranian manufacturing industries at ...