Survival data

Survival data focuses on whether or not an object in a study experiences an event. In addition, the follow-up time is also considered. Time zero or time origin is the time when the study starts. Depending on the purpose of a study, time zero or time origin can be different. For instance, in a prostate cancer study, researchers recruit 40-year-old and older male participants, but in a study of puberty developmental ages, male and female teenagers of 12 and older are recruited. If the research takes place over a period of time (which could be several months or years) then recording the time origin and follow-up time during the study is vitally important.

Lastly, we discuss the relationship between survival and censoring times and how we record survival data with censoring. Suppose that for each object in a sample, we know its true event time T and true censoring time C. Then, the survival time of an object is the period of time until an event occurs and the censoring...