In general, 50 percent of people use the phrase "a couple" only when referring to exactly two of something. But among those who use disposable plates/cups more often than non-disposable plates/cups, 77 percent use the phrase "a couple" only when referring to exactly two of something.
Based on a survey of 47 people who use disposable plates/cups more often than non-disposable plates/cups and 467 people total.