How to Calculate Frequency in a Normal Distribution?

[zgochenour]

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.

 

[bpet]

They are normally distributed (exactly) ... 1000 of them are 100kg.

If they are exactly normally distributed then none would be 100kg. Did you mean to say that 1000 of them are in the interval (99.5,100.5) ? Once you work out the probability of this interval you can compare it to that of the other interval to get an idea of the relative expected frequencies.

Some other things to keep in mind for your calculator are sensitivity to parameter values and observed frequency vs expected frequency.