The SAT will remain a “norm-referenced” exam, designed primarily to rank students rather than measure what they actually know. Such exams compare students to other test takers, rather than measure their performance against a fixed standard. They are designed to produce a “bell curve” distribution among examinees, with most scoring in the middle and with sharply descending numbers at the top and bottom. Test designers accomplish this, among other ways, by using plausible-sounding “distractors” to make multiple-choice items more difficult, requiring students to respond to a large number of items in a short space of time, and by dropping questions that too many students can answer correctly.

“Criterion-referenced” tests, on the other hand, measure how much students know about a given subject. Performance is not assessed in relation to how others perform but in relation to fixed academic standards. Assuming they have mastered the material, it is possible for a large proportion, even a majority, of examinees to score well; this is not possible on a norm-referenced test. K-12 schools increasingly employ criterion-referenced tests for this reason. 

https://www.nytimes.com/2015/05/05/opinion/the-big-problem-with-the-new-sat.html