Puasson teoremasi — bu qisqa muddatli hodisalar soni vaqti davomida hodisalar yuzaga kelish ehtimolligini aniqlaydi. Agar λ\lambdaλ hodisalar soni vaqti davomida hodisalar soni nnn ga yaqin bo'lsa, unda Puasson teoremasi bilan yordamida hodisalar soni yuzaga kelish ehtimolligi P(n;λ)=e−λ⋅λnn!P(n; \lambda) = \frac{e^{-\lambda} \cdot \lambda^n}{n!}P(n;λ)=n!e−λ⋅λn​