background: the aim of this study is to evaluate the association between different treatments and survival time of breast cancer patients using either standard cox model or stratified cox model. methods: the study was conducted on 15830 women diagnosed with breast cancer in british columbia, canada.  they were divided into eight groups according to patients’ ages and stage of disease either cox...

tires represent a critical spare part in mines. there is a shortage of medium and large tires. in addition, with increased mining activities and the creation of new mines, the demand for tires has increased significantly. thus, it is particularly important for mining engineers to identify tire characteristics and correctly manage the spare part inventory. spare parts management is critical from...

the waiting time between children births are called tempo. this phenomenon plays a crucial role in the child and mother health. the purpose of the present study is determination of factors which influence this variable of interest. a significance level of 5% and power of 80% considered to calculate the required sample size for this cross sectional study. the sample size of 124 women determined ...

objective: tempo is the average waiting time to next birth for a woman. role of fertility as the most important phenomenon determining population fluctuations due to the studies of it compared with other demographic phenomena be important and review the multifarious socioeconomic factors of it share  a large effective population studies. general purpose of this study is fitting the cox model to...

In this paper, we are concerned with the estimation of the discrepancy between two treatments when right-censored survival data are accompanied with covariates. Conditional confidence intervals given the available covariates are constructed for the difference between or ratio of two median survival times under the unstratified and stratified Cox proportional hazards models, respectively. The pr...

background: cox proportional hazard (cph) model is the most widely used model for survival analysis. when there are unobserved/unmeasured individuals factor, then the results of the cox proportional hazard model may not be reliable. the purpose of this study was to compare the results of cph and frailty models in breast cancer (bc) patients. methods: a historical cohort study was carried out us...

this study was designed to investigate causes of culling in industrial dairy herds in fars province and to describe the pattern of reason-specific culling with respect to age of animal and interval from calving to culling. a total number of 9 dairy herds were selected for the study and information about culling reasons, birth date, last calving date and culling date was collected for culled cow...