In: Statistics and Probability
In Example 6.33 we found the distribution of the sum of two i.i.d. exponential variables with parameter λ. Call the sum X. Let Y be a third independent exponential variable with parameter λ. Use the convolution formula 6.8 to find the sum of three independent exponential random variables by finding the distribution of X + Y.
Answer:
Given Data
we found the distribution of the sum of two i.i.d. exponential variables with parameter λ.
Let Y be a third independent exponential variable with parameter λ.
x = sum of two expoential distribution.
distribution
and distribution
let pdf of x be f(x)
and pdf of y be g(y)
need to find pdf of z = x + y
so let pdf of z be h(z)
then by convolution formula:
now
, ,
,
so
Hence
,
so distribution
same way it can be proven that distribution
if each distribution.