Even among 18-21 year old college american women there are ridiculous amounts of variables that you can't control for. Give up the idea that you can control for

Even among 18-21 year old college american women there are ridiculous amounts of variables that you can't control for. Give up the idea that you can control for biases in psychology. Do big mixed tests, then if there's positive outcomes see if its correlated to any of those groups. Then you can do more tests on the groups that didn't respond.