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Converting Test Scores into Marks

This policy should be read in conjunction with: 

As explained on our Numerical Marking: General Principles page, none of our marking is quantitative, so quantitative scores normally need to undergo conversion to become marks. 

Some assignments, like language tests, might produce quantitative scores. Those scores are not the marks for that assignment. In principle, they will always need to go through some process of conversion – where conversion involves making qualitative judgments about what is meant by different levels of achievement in a quantitatively scored test, and then translating those qualitative judgments into numerical marks in the normal way. 

For instance, imagine that there is a multiple-choice test with 100 questions, which straightforwardly yields a score between 0 and 100. There is absolutely no reason, in principle, why the mark that the student should get for that assignment should be identical to this numerical score, because (for instance) there is no reason to think that an ability to get 40 questions out of a 100 right on this test must match the qualitative criteria we have for gaining a pass mark, and no reason to think that an ability to get 70 right matches the qualitative criteria we have for first class work. It might be, rather, that on this simple multiple-choice questionnaire, we judge that a student needs to get a score of 80 out of 100 to pass (and so to deserve a mark of 40), but that if he or she gets the maximum score of 100 out of 100, he or she is achieving really excellent first class quality (and so deserves a mark of 85). Some formula will therefore be needed to convert the numerical score into an appropriate mark, in the light of these judgments. 

This might well mean that marks from such a test are effectively capped. In the example just given, the test cannot yield marks above 85. That is not an awkward mathematical problem: it is a recognition that some forms of assignment simply don’t allow students to demonstrate the extraordinary levels of penetrating insight that we recognise with the very highest marks. 

It is sometimes possible to design a test that yields quantitative scores in such a way that (i) getting a score of 40 does equate qualitatively to a pass; (ii) getting a score of 70 or more really does smell qualitatively of ‘first class’ work in a way that lower scores do not; (iii) it is very difficult indeed to get a score of more than 85; (iv) it is well-nigh impossible (or perhaps actually impossible) to get a score of more than 90. These scores might be actual percentages (i.e., the number might represent the proportion of items on the test that the student has got right), or (more plausibly) they might be yielded by some more complex numerical scoring system. But if they match the qualitative criteria in the way suggested, the mark awarded could be the same numerical value as the score. 

If quantitative tests are used, it is good to design them in the way just described, so that conversion can be avoided – because score conversion can cause confusion and upset, if the reasons for it are not well understood by all involved. Where such test design is not possible, however, numerical scores do need to be converted.