Distribution Theory : key informaiton
Determine the distribution of Y = X_1 + X_2 + . . . + X_n by first determining the joint distribution of
Z_1 = X_1
Z_2 = X_1 + X_2
Z_3 = X_1 + X_2 + X_3
.
.
.
Z_n = X_1 + X_2 + X_3 + . . . + X_n
and then computing the marginal distribution of Z_n
According to my text book:
Exp(a), a>0 has density
f(x)=(1/a)e^(-x/a), x>0
and E[X]=a Var(X)=a^2 and the characteristic function is phi x(t)=1/(1-ait)
This is all the information I have regarding this problem. I hope its enough for someone. I have no idea what to do with this and I need a detailed step by step answer if possible.