Proof isn't required. It's difficult to prove because it's difficult to state clearly what is "better" and it's expensive to collect preference data (or simila

Proof isn't required. It's difficult to prove because it's difficult to state clearly what is "better" and it's expensive to collect preference data (or similar). You could use common sense after looking at lots of samples and say "this method seems to work better if you are trying to optimize for X".