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

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

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  • MacKenzie, Gilbert; Pan, Jianxin (IWSM, 2001)
    Pourahmadi (1999) provided a convenient reparameterisation of the marginal covariance matrix arising in longitudinal studies. We exploit his work to model the dependence of this covariance structure on baseline ...
  • 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 ...
  • MacKenzie, Gilbert; Do Ha, II (IWSM, 2007)
    We revisit the crossing hazards problem in survival analysis and compare the use of Cox's semi-parametric model with a parametric non-PH model from the generalised time-dependent logistic family(GTDL). A set of gastric ...
  • 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 ...
  • Burke, Kevin (University of Limerick, 2014)
    In general, parametric regression models can be motivated by allowing the parameters of a probability distribution to depend on covariates. Furthermore, it is standard practice to relate covariates to one parameter of ...
  • Al-tawarah, Yasin; MacKenzie, Gilbert (IWSM, 2003)
    In longitudinal studies with a set of continuous or ordinal repeated response variables it may be convenient to summarize the outcome as a threshold event. Then, the time to this event becomes of interest. In this paper ...
  • MacKenzie, Gilbert; Do Ha, II; Lee, Youngjo (IWSM, 2003)
    Correlated survival times may 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 (GTDL) ...
  • 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 ...
  • Al-tawarah, Yasin; MacKenzie, Gilbert (IWSM, 2005)
    In this paper we investigate the use of accelerated Weibull hazard model. We compare it with Logistic Accelerated Hazard model. The models are used to analyze survival data from the Northern Ireland lung cancer study ...
  • 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 ...
  • Peng, Defen; MacKenzie, Gilbert (IWSM, 2007)
    We develop an analysis of the reliability of reliability data following a negative exponential distribution and subject to type I censoring. Our main focus is to determine the role of the particular analytical approach ...
  • 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 ...
  • Blagojevic, Milica; MacKenzie, Gilbert (IWSM, 2004)
    We generalize the previously developed Non-PH CTDL-Gamma and the PH Weibull-Gamma frailty models to correlated survival data. In particular, we seek analytical results using the marginal approach, to determine whether ...
  • 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, ...
  • Patterson, Richard; MacKenzie, Gilbert (IWSM, 1999)
    In recent years the tangent distance approach of Simard et al (1993) to pattern recognition tasks such as handwritten character recognition has proven successful. Simard's distance measure could be made locally invariant ...
  • 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 ...
  • MacKenzie, Gilbert; Xu, Jing (IWSM, 2009)
    The history of space-time clustering concepts and methods are re- viewed briefly. The space-time clustering model of Ederer et al is investigated in detail. This method has been used extensively in the epidemiological ...

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