I am trying to create a calculator that let's a user provide the standard deviation, mean, frequency at that mean, and range of values - then the calculator will give the frequency in that value range. For instance, purely illustrative -- say you know the mean weight for some group is 100kg. They are normally distributed (exactly) around that mean with a standard deviation of 10kg. 1000 of them are 100kg. How many of the group are between 112kg and 116kg. I hope that makes sense. Thanks for the help. I'm not really sure where to begin.