This weekend we’ll add a little statistics to our ongoing Sunday tour of the zoo of mathematical functions!
This is the Poisson distribution for λ = 4. To be formally correct, it’s only defined for integer values. This pops up in physics all the time in the context of counting discrete events with independent probabilities. For instance, if you have a sample of a long-lived radioactive isotope and you see on average 4 decays per minute, during any given minute the probability of seeing k decays is given by the formula above.