A major assumption of the Cox proportional hazards model is that the effect of a given covariate does not change over time. If this assumption is violated, the simple Cox model is invalid, and more sophisticated analyses are required. This paper describes eight graphical methods for detecting violations of the proportional hazards assumption and demonstrates each on three published datasets wit...

Background: The age at first birth corresponds to the of mother giving child. study aims accessing determinants timing among Ethiopian women.
 Methods: data for this was extracted from published reports Demographic and Health Survey. used15, 683 women aged 15-49 years nine regions two city administrations. Cox Proportional hazards model used identifying factors associated with birth.
...

The burden of cancer is increasing very rapidly day by all over the world, largely due to an unhealthy lifestyle. Some cross-sectional studies have been conducted on lifestyle patients based Sylhet city, Bangladesh. However, best our knowledge, no study has done longitudinal aspect considering whole Bangladesh, therefore, we aimed conduct a know effects and heritability in We selected total 384...

Prognostic models are often used to estimate the length of patient survival. The Cox proportional hazards model has traditionally been applied to assess the accuracy of prognostic models. However, it may be suboptimal due to the inflexibility to model the baseline survival function and when the proportional hazards assumption is violated. The aim of this study was to use internal validation to ...