One can use this calculator to calculate cumulative probabilities of questions/problems that can be solved with normal distribution. For example, what is the probability of this gas station selling at least 18 thousand gallons of gasoline today? Given it have an average sale of 16.7 thousand gallons per day and a standard deviation of 2.3 thousand gallons.Normal distribution is a useful distribution used in many industries: Health, Medical, Oil, Business Intelligence and so on