Variance Let be the sum of random number of random variables, i.e., , where is the random number and are the random variables which are i.i.d.
Similarly we find the variance
Now , hence . Using these results and replacing them in (3.1) we have
Thus
be the sum of random number of random variables, i.e., 
, where 
is the random number and 
are the random variables which are i.i.d.
,
. 
as 
