This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Kaplan meier methods is used for 
Select and explain. 
A. Survival, B. Prevalance, C. Incidence, D. Frequency
A: Survival
Answer: A: Survival 
Explanation: The Kaplan-Meier estimator, also known as the product limit estimator, is a non-parametric statistic used to estimate the survival function from lifetime data. In medical research, it is often used to measure the fraction of patients living for a ceain amount of time after treatment.