Background: I am a Mechanical Engineer working as an Industrial Engineer. I have collected some data that is the amount of time that an event took to complete. I first assumed it would be normally distributed, but after plotting a histogram and a normal distribution with the data, I doubt that the set follows a normal distribution. So lets do a little thought experiment. What is the probability of the event taking from -2 to 0 second? I would say it would be zero. What is the probability of the event taking taking from negative infinity to zero seconds? I would say it would be zero. So I think it is save to say that the domain of the distribution is from 0 to infinity. Question: What are some models tailored for time distribution? I would say a time distribution should have a domain that goes from 0 to infinity.