Utilizing cumulative logit models and human computation on automated speech assessment

• Authors: Lei Chen
• Venue: Proceedings of the Seventh Workshop on Building Educational Applications Using NLP
• Year: 2012

We report two new approaches for building scoring models used by automated speech scoring systems. First, we introduce the Cumulative Logit Model (CLM), which has been widely used in modeling categorical outcomes in statistics. On a large set of responses to an English proficiency test, we systematically compare the CLM with two other scoring models that have been widely used, i.e., linear regression and decision trees. Our experiments suggest that the CLM has advantages in its scoring performance and its robustness to limited-sized training data. Second, we propose a novel way to utilize human rating processes in automated speech scoring. Applying accurate human ratings on a small set of responses can improve the whole scoring system's performance while meeting cost and score-reporting time requirements. We find that the scoring difficulty of each speech response, which could be modeled by the degree to which it challenged human raters, could provide a way to select an optimal set of responses for the application of human scoring. In a simulation, we show that focusing on challenging responses can achieve a larger scoring performance improvement than simply applying human scoring on the same number of randomly selected responses.