-{\displaystyle P(k{\text{ events in interval}})=e^{-\lambda }{\frac {\lambda ^{k}}{k!}}}
+P(k{\text{ events in time period}})=e^{-\frac{\text{events}}{\text{time}}*\text{time period}} * \frac{(\frac{\text{events}}{\text{time}}*{\text{time period}})^{k}}{k!}
+
+P(k{\text{ events in interval}})=e^{-\lambda }{\frac {\lambda ^{k}}{k!}}