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Browsing Centres Science and Engineering by Author "MacKenzie, Gilbert"

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Browsing Centres Science and Engineering by Author "MacKenzie, Gilbert"

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  • MacKenzie, Gilbert; Peng, Defen (2014)
    In the parametric regression models with categorical covariates, it is well known that many key quantities of interest are invariant to the choice of reference subclass. However, surprisingly, not all quantities are ...
  • MacKenzie, Gilbert; Greig, Mary; Hay, Iris; Pemberton, John (BMJ Publishing Group, 2016)
    Background The 5-year follow-up results for the 1202 middle-aged men prospective study of CHD incidence were published in 1980. This paper extends the follow-up, relating the development of CHD to ten risk factors. Methods The ...
  • Sheikhi, Ali; Ramsey, David; MacKenzie, Gilbert (2011)
    A selective sweep occurs when a positive mutation spreads through a population. It causes a reduction in variation among the nucleotides in the neighbourhood of the mutation. Whether or not a selective sweep has occurred can ...
  • Kiri, Victor A; MacKenzie, Gilbert (Bentham Science Publishers, 2009)
    Although cohort studies which are based on intention-to-treat (ITT) approach offer a simple design with data which are simpler to analyse and results easier to interpret, such studies also intrinsically assume that any ...
  • MacKenzie, Gilbert; Peng, Defen (IWSM, 2010)
    We present a general likelihood for interval censored survival data arising in longitudinal studies such as longitudinal randomized controlled clinical trials (RCTs) and give some general formulae for inference in ...
  • MacKenzie, Gilbert; Conde, Susana (IWSM, 2016)
    We develop a Smooth Lasso for sparse, high dimensional, contingency tables and compare its performance with the usual Lasso and with the now classical backwards elimination algorithm. In simulation, the usual Lasso had ...
  • Conde, Susana; MacKenzie, Gilbert (IWSM, 2011)
    We consider several least absolute shrinkage and selection operator (LASSO) penalized likelihood approaches in high dimensional contingency tables and with hierarchical log-linear models. These include the proposal of a ...
  • Conde, Susana; MacKenzie, Gilbert (IWSM, 2012)
    We compare improved classical backward elimination and forward selection methods of model selection in sparse contingency tables with methods based on a regularisation approach involving the least absolute shrinkage ...
  • Xu, Jing; MacKenzie, Gilbert (Oxford University Press, 2012)
    It can be more challenging and demanding to efficiently model the covariance matrices for multivariate longitudinal data than for univariate case because of the correlations between responses arising from multiple variables ...
  • Xu, Jing; MacKenzie, Gilbert (IWSM, 2010)
  • Xu, Jing; MacKenzie, Gilbert (IWSM, 2009)
    A data-driven method for modelling intra-subject covariance matrix is introduced to constrained marginal models with longitudinal data. A constrained iteratively re-weighted least squares algorithm is presented ...
  • Burke, Kevin; MacKenzie, Gilbert (IWSM, 2013)
    The proportional hazards (PH) assumption in survival analysis may not always be appropriate. If data do not obey the assumption then we will reach incorrect conclusions by making it. For example we may find a covariate to ...
  • Burke, Kevin; MacKenzie, Gilbert (IWSM, 2012)
    It is well known that the proportional hazards (PH) assumption is a simplifying assumption in survival analysis that may not always be appropriate. However, PH models are routinely fitted and inference is made on the ...
  • MacKenzie, Gilbert; Al-tawarah, Yasin; Blagojevic, Milisa; Burke, Kevin (IWSM, 2018)
    Non-PH parametric survival modelling is developed within the frame- work of the multiple logistic function. The family considered comprises three basic models: (a) a PH model, (b) an accelerated life model and (c) a model ...
  • Lynch, Joseph; MacKenzie, Gilbert (IWSM, 2011)
    We compare and contrast the properties of the bivariate Weibull and GTDL regression survival models. An analytic expression for the correlation between times is derived for the Weibull model and a modified Kullback-Lei ...
  • Louzada-Neto, Francisco; MacKenzie, Gilbert; Cremasco, Caroline Pires; Ferreira-Silva, Paulo Henrique (UNESP, 2011)
    In order to accommodating crossing hazard curves, which are non- proportional hazards, we consider in this paper a generalized time-dependent logistic hazard survival model, which has a time-dependent term. The model is ...
  • Peng, Defen; MacKenzie, Gilbert (IWSM, 2011)
    Recently, several advances have been made in the analysis of interval censored (IC) data mainly in relation to semi-parametric proportional hazard (PH) models (Gómez et al., 2009, Lesaffre et al., 2005). It is arguable, ...
  • Do Ha, II; MacKenzie, Gilbert (SAGE Publications, 2010)
    Correlated survival times can be modelled by introducing a random effect, or frailty component, into the hazard function. For multivariate survival data we extend a non-PH model, the generalized time-dependent logistic ...
  • MacKenzie, Gilbert; Do Ha, II (IWSM, 2013)
    The focus is mainly, but, not solely, on longitudinal randomised controlled clinical trials. The paper aims to delineate the role of frailty in the modern analysis of such trials and also in longitudinal survival studies. ...
  • Louzada-Neto, Francisco; Cremasco, Caroline Pires; MacKenzie, Gilbert (Gowas Publishers, 2010)
    Lifetimes which satisfy a non-proportional hazard model may arise in several areas, such as, Medicine, Biometrics, Criminology and Industrial Reliability. For these data it is reasonable to presume that the hazard function ...

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