Dear friends,

Is there any known bound on sum of independent but not identically distributed geometric random variables? I have to show that the tail of the sum drops exponentially (like in the Chernoff bounds for the sum of iid geom. variables).

Formally, if $X_i$ ~ Geom($p_i$), and $X = \sum_{i=1}^n X_i$, and it is known that $E[X]=\Theta(n)$,

Is it possible to show that $\Pr(X < 2E[X]) > 1 - \delta ^n$, where $\delta < 1$?

Thank you in advance, Michael.