Survival is the ability of a living thing to keep alive. It may refer to the act of surviving a catastrophe, or the continued existence of an animal after a severe injury. The survival of an animal is usually associated with the ability of that animal to find food and water.
A survivor function is a mathematical model that directly describes the survival experience of a study cohort. This model is typically calculated by a KM (or KM averaging) estimator, and uses event times to calculate the probabilities of each group.
One of the most common methods of calculating the survivor function is a logrank test. This is a statistical procedure that tests for differences between a curve with a high probability of being true and a curve with a low probability of being true.
Another is a hazard function. An h(t) or l(t) is a probability distribution that represents the probability that a particular event occurs at a particular time.
For a medical researcher, the hazard function is an important tool for estimating probabilities of survival. It can also be used as a diagnostic tool taraftarium24.
The survivor function is a complicated concept that must adjust for a number of patient-related factors. As a result, the hazard function does not always fit a straight line, as it is rarely normally distributed.
A KM averaging technique can be used to estimate the median survival time of a patient. It is not as precise as the logrank test, and is best used for subgroups of data that have a similar survival rate.