Survival Analysis with Exponential and Gamma Distributions
Learn about exponential and gamma distributions for modeling waiting times and Poisson processes. Calculate probabilities and expected values. Ideal for studying radioactive decay and inter-arrival times.
Survival Analysis with Exponential and Gamma Distributions
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Presentation Transcript
Exponential Distribution • The RV T has an exponential distribution with rate l (for l > 0) if T has the probability density • The mean and standard deviation of T are
Exponential Distribution • The exponential distribution is used to model waiting times for the occurrence of some event (death, failure, mutation, radioactive decay, etc.). • The continuous analog of the geometric distribution. • Models the successive inter-arrival times of a Poisson process in time.
Suppose a particular kind of radioactive atom has a half-life of 2 years. Find • The probability that an atom of this type survives at least 5 years. • The time at which the expected number of atoms is 10% of the original amount.
Gamma Distribution • If Tr is the time of the rth arrival after t = 0 in a Poisson process with rate l, then Tr has the gamma (r, l) distribution with probability density • The mean and standard deviation of Tr are