To analyse how much time you expect between random arrivals, we can use the exponential pdf.
The data is the number of counted ( such as hockey goals ) over a given time interval (in minutes).
You can then enter a time of concern, and calculate the probability that the time between arrivals is < the
time of concern.

Research the exponential distribution. Find out it's mean and standard deviation.
Identify an integral for evaluating the probability calculated above.