Normalize data from different groups

Question

I have data that has been grouped into 27 groups by different criteria. The reason for these groupings is to show that each group has different behavior. However, I would like to normalize everything to the same scale. For example, I would like to normalize to a 0-1 scale of 0-100, that way I could say something like $43^{rd}$ 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, would this work? Would I have to calculate the mean/standard deviation of all of the combined data or do each of the 27 groups individually?

Answer 1

You can normalize each criteria independently in values between 0 and 1 without taking into account the other criterias, it will work better for most classification methods k-nearest neighbors, random forest, neural network, etc.

$$x^*_{i,j}=\frac{x_{i,j}-x^{min}_j}{x^{max}_j-x^{min}_j}$$