1. The problem statement, all variables and given/known data I teach a class of statistics with students who often do not have the types of calculators that can calculate standard deviation and who do not know how to program Excel, but do have access to the Internet. Googling "standard deviation calculator" on the Internet gives me calculators which are not for grouped data, so cannot be used to calculate if the data is in a frequency table with a large amount of data points in each category. Any alternatives?, short of programming it myself? (once in Windows Excel, once in Mac Excel)? 2. Relevant equations For example, http://ncalculators.com/statistics/mean-standard-deviation-calculator.htm http://www.mathsisfun.com/data/standard-deviation-calculator.html http://easycalculation.com/statistics/standard-deviation.php https://statistics.laerd.com/calculators/standard-deviation-sample-population-calculator.php http://www.calculator.net/standard-deviation-calculator.html 3. The attempt at a solution I have tried to find ways to "tweak" the input, but e.g. multiplying all the data by something gives me a sort of "uncertainty principle": I could get the mean right, but that would throw off the s.d.