The number of traffic accidents at a certain intersection is thought to be well modeled by a Poisson process with a mean of 3.5 accidents per year.
Find the mean waiting time between accidents and find the standard deviation of the waiting times between accidents.
I assumed $\mu$ = $\lambda$ and $\sigma$$^2$ = $\lambda$, but that didn't seem to work. I've been looking at multiple formulas, including the Poisson ones, and I can't figure out how to even begin to figure this out. I could use a step in the right direction