I need to calculate tolerance intervals in Excel. I would prefer the calculation for a regression, but will try figure out how to use a population tolerance interval with a regression if that is all that is available. I should be able to set the following for the calculation: Confidence Level (CL), % of population (%P) and whether it is an upper, lower or two-sided tolerance interval (Type). That is, I might want to do a calculation using an upper tolerance interval the shows with 95% confidence that 99% of the population will be within that bound. Then maybe I want to change it to 99%CL., 99.9%P and 2-sided interval. Can anyone help me with this? I would prefer doing it with cell formulas (it can be set up with different formulas in differnt cells to get the final answer in other cells), but will use VBA code if necessary. Thank you in advance for your help. I have attached a article I found on tolerance intervals for regression and the data he used for the example, if anyone feels that can apply it to Excel. I have not been able to yet.