What is the difference between the hazard function, survival function, and retention rate in survival analysis?
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asked Apr 26, 2015 at 20:12
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1$\begingroup$ What does your book say about these things? $\endgroup$– Dilip SarwateApr 26, 2015 at 20:22
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1$\begingroup$ I don't have a book. my professors are not fully explaining. is there a book you can recommend? $\endgroup$– Amanda Christina WashingtonApr 26, 2015 at 23:47
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2 Answers
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Hazard Function/Hazard Rate,say, $\lambda_i$:- probability of life not survive in the $i^{th}$ time interval($t_i-t_{i-1}$).
Survival Function,$S(t_i)$:- probability of life survive upto $t_i$.
Retention Rate,$1-\lambda_i$:- probability of Life survive in $i_{th}$ time interval($t_i-t_{i-1}$).
Relations:-
Relation between hazard rate and retention rate remains same(Retention Rate=1- Hazard Rate)
But relation with Survival Function may differ, like in Kaplan-Meier method $S(t_i)=\prod_i (1-\lambda_i)$ and in Nelson-Aalen $S(t_i)=exp(-\sum_i\lambda_i)$
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Using testing light bulbs on a daily basis for example. (You count how many fail a day)
Hazard rate ---- 'Failures'/'number of current good bulbs' by day.
Survival rate ---- Proportion of the ones the remain OK by day.
Retention rate ---- 1 - 'hazard rate'
Plot the rates v.s. time(days) you get the functions.
