Data ageing: a technique for discounting old data during student modelling

Student modelling systems must operate in an environment in which a student’s mastery of a subject matter is likely to change as a lesson progresses. A student model is formed from evaluation of evidence about the student’s mastery of the domain. However, given that such mastery will change, older evidence is likely to be less valuable than recent evidence. Data ageing addresses this issue by discounting the value of older evidence. This paper provides a formal evaluation of the effects of data ageing. While it is demonstrated that data ageing can result in statistically significant increases in both the number and accuracy of predictions that a modelling system makes, it is also demonstrated that the reverse can be true. Further, the effects experienced are of only small magnitude. It is argued that these results demonstrate some potential for data ageing as a general strategy, but do not warrant employing data ageing in its current form.