I have data that have been grouped in 27 groups by different criteria. The reason for these groupings is to show that each group has a different behavior. However, I would like to normalize everything to the same scale. For example, I want to normalize to a 0-1 scale or 0-100, that way I could say something like 43rd percentile and it would have the same meaning across groups. If I were to just, say, standardize each individually by subtracting the mean of each and dividing by standard deviation work? Would I have to calculate the mean/st. dev of all of the combined data or do each of the 27 groups individually?