Math CentralQuandaries & Queries


A program consists of two modules executed sequentially. Let f1(t) and f2(t) respectively denote the probability density functions of time taken to execute the two modules. The probability density function of the overall time taken to execute the program is given by
(1) f1(t) + f2(t)
(2) INTEGRAL OF(f1(x)f2(x)dx) from 0 to t

(3) INTEGRAL OF(f1(x) f2(t-x) dx) from 0 to t

(4) max{f1(t), f2(t)}

I am Ravinder from G.N.D.U INDIA

Hi Ravinder,

The answer is (3), so-called convolution of the sum of two independent random variables. All other operations will not produce a density function.


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