Introduction

Survival analysis is also known as duration analysis, transition analysis, failure time analysis, and time-to-event analysis. In survival analysis, subjects are tracked until an event happens or we lose them from the sample. Events can be anything, such as death, marriage, divorce, and so on. Subjects are followed for a specific time and the focus is on the time the event occurs. The three terms used commonly while talking about survival analysis are birth event, death event, and censorship. A birth event is the time when the observation started, a death event is the time at the end of the event or study, and censorship means a death event will not always occur. Censoring occurs because the subject does not experience the event during the time, the subject is lost, or the subject withdraws from the study. Censoring can be thought of as a kind of missing data problem. Consider the study of a clinical trial being conducted for 2 years; if the person under observation does not...