[nonameiguess]

The only way this could even conceivably be done in a scientifically valid way is randomized controlled trials, which would mean not giving the same interviews to all candidates, which is only possible if hiring at a large enough scale as to even be able to sample meaningfully from multiple "interview type" groups, and it would of course require it to be legal to give different interviews at random, which I'm not sure is true. I guess as long as it's actually random, you're not discriminating against any specific group, but it isn't exactly fair and you risk killing goodwill of your employees when they realize you're running experiments on them.

Of course, it's really not possible at all to do this at the level of rigor expected of, say, clinical trials. Each new hire will know what type of interview you put them through, and there is no reliable way you can prevent them from telling others.