!$ F(K) = { \large \theta^K.e^{- \theta} \over K!}; E(X) = \theta\,e\,V(X) = { \large k. \theta \over 2} !$

!$ F(K) = { \large \theta^K.e^{- \theta} \over K!}; E(X) = \theta\,e\,V(X) = \theta^2 !$

!$ F(K) = { \large \theta^K.e^{- \theta} \over x!}; E(X) = { \large \theta \over 2}\,e\,= \theta !$

!$ F(K) = \sum_{x=0}^{K} { \large \theta^K.e^{- \theta} \over x!}; E(X) = \theta\,e\,V(X) = \theta !$

!$ F(K) = \sum_{x=0}^{ \infty} { \large \theta^K.e^{- \theta} \over x!}; E(X) = K\,e\, = { \large K \over 2} !$