 The easiest and most common is to disqualify listeners who rate the hidden reference below 90 MUSHRA points for more than 15 percent of all test items.The hidden reference should be rated with 100 MUSHRA points so this is obviously a mistake.While it can happen that the hidden reference and a high-quality signal are confused, a rating of lower than 90 should only be given when the listener is certain that the rated signal is different than the original reference.