and the results are affected but you don't know why Well, that's just your assumption without knowing the exact problem and I think you are missing my point.

and the results are affected but you don't know why Well, that's just your assumption without knowing the exact problem and I think you are missing my point. You can approach to data preparation by randomly changing things, and maybe you can get some interesting results but I promise you you will fail many many times. Other way is to know what does it means to change the mean for the median for instance (as I mentioned in this just random example), and I promise you will find better solutions. The idea is not just "change and test" and see what happens. The interesting part is to understand how the model uses your representation and why one is "better" than another.