Science exams are typically examples of the difficulty model of assessment where answers are right or wrong (see Christodoulou, Making Good Progress chapter 3). Assessors can use a marking rubric to judge whether an answer reaches a threshold of ‘correctness’ and award or deny a mark.
For many answers, this will be uncontroversial. However, some answers are less wrong than others: some answers are better than wrong.
A colleague and I took a single sentence answer from an end of year exam that many students got wrong, but which weren’t uniformly wrong.
A mark-scheme is binary: right or…
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