what is used to calculate normal frequency distribution
That is, RAND() generates random probabilities. Therefore, you can use the NORM.INV function to calculate a random number from a normal distribution, using this formula in Excel 2007 and above... =NORM.INV(RAND(), mean, standard_dev). ...and this formula in Excel 2003...he standard deviation of a sample is a measure of the spread of the sample from its mean. (We're taking about many items in a sample, of course, not just a single item.) In a normal distribution, about 68% of a sample is within one standard deviation of the mean.