%0 Journal Article %A Saki Malehi, Amal %A Hajizadeh, Ebrahim %A Ahmadi, Kambiz %T Weibull Frailty Model in Survival Analysis: An Application to Colorectal Cancer Patients %J Journal of Statistical Sciences %V 6 %N 1 %U http://jss.irstat.ir/article-1-170-en.html %R %D 2012 %K Survival Analysis, Subject Specific Random Effects, Frailty Models, Weibull Distribution, Power Variance Function Distribution, %X The survival analysis methods are usually conducted based on assumption that the population is homogeneity. However, generally, this assumption in most cases is unrealistic, because of unobserved risk factors or subject specific random effect. Disregarding the heterogeneity leads to unbiased results. So frailty model as a mixed model was used to adjust for uncertainty that cannot be explained by observed factors in survival analysis. In this paper, family of power variance function distributions that includes gamma and inverse Gaussian distribution were introduced and evaluated for frailty effects. Finally the proportional hazard frailty models with Weibull baseline hazard as a parametric model used for analyzing survival data of the colorectal cancer patients. %> http://jss.irstat.ir/article-1-170-en.pdf %P 69-82 %& 69 %! Frailty Models in Survival Analysis %9 Applied %L A-10-415-1 %+ Department of Biostatistics, Tarbiat Modares University, Tehran, Iran. %G eng %@ 1735-8183 %[ 2012