Using NLP to support scalable assessment of short free text responses

Marking student responses to short answer questions raises particular issues for human markers, as well as for automatic marking systems. In this paper we present the Amati system, which aims to help human markers improve the speed and accuracy of their marking. Amati supports an educator in incrementally developing a set of automatic marking rules, which can then be applied to larger question sets or used for automatic marking. We show that using this system allows markers to develop mark schemes which closely match the judgements of a human expert, with the benefits of consistency, scalability and traceability afforded by an automated marking system. We also consider some difficult cases for automatic marking, and look at some of the computational and linguistic properties of these cases