# Math Help - a stupide question

1. ## a stupide question

In the process of proving "sums of a finite number of independent Poisson rv's is a Poisson rv", why do we use moment-generating function or probability generating function ? I am confused wtih the use of mgf or pgf.. Anyone can explain it ? thx

2. Originally Posted by solskjaer
In the process of proving "sums of a finite number of independent Poisson rv's is a Poisson rv", why do we use moment-generating function or probability generating function ? I am confused wtih the use of mgf or pgf.. Anyone can explain it ? thx
Because it makes the calculation much easier. Try doing it another way (eg. using convolutions to get the pdf of a sum of random variables) ......