In India, the criteria for college admissions is very unambiguous and the question of whether you study in a prestigious institutions or not boils down to whether you score well in a standardized exam (e.g., institutions like IIT, AIMS, NITS etc....with some notable exceptions like BITS and VIT).
In USA, there was a related idea with tests (e.g., the SAT, GRE) being used. I infer that these are 'benchmark' tests rather than competitive tests since there is no relative grading and marking is absolute. However, in recent times we can see that the country as a whole is moving away from considering test scores to seeing a student's essays and their personal accomplishments. This was heightened in 2021 where many top colleges dropped standardized testing requirements completely. This leads, in my opinion, to a highly ambiguous admission process.
Between all these different philosophies underlying admissions, was any research put in attempting to find what would be objectively the best criteria / method to choose students? What were its findings?
In essence, I am asking if there is some science which can be used to figure out what is the best admissions procedure. I am not asking for metrics based on personal feelings, but rather from systematic unbiased scientific studies.
This post is in regards to any very competitive admissions process (college, grad school, internship, ...). In less competitive environments (e.g., lower ranked colleges), admission is almost certain if you have just have some minimum quals, and so any aspect of ambiguity is gone.