“…All 76 reviewed articles included comparisons that can be grouped into one of eight categories (Figure 5). In 23 articles (30.3 %), the comparison was across levels of participants' performance, for example, high vs. low performers [19], [23], [25], [50], [74], [76], [86], student competency level [69], [102], quality of ideas [46], [73], learning outcomes [80], [83] , positive vs. negative gain [82], proficiency level [68], accuracy level [96] and correct graph solving [95].…”