Human-Machine Hybrid Peer Grading in SPOCs

Peer grading, allowing students/peers to evaluate others’ assignments, offers a promising solution for scaling evaluation and learning to massive open online courses (MOOCs) and small private online courses (SPOCs). In the environment of MOOCs, due to the varied skill levels and attitudes of online students, it is not easy for the students to present fair and accurate scores for their peers’ assignments. Recently, statistical models have been proposed to improve the fairness and accuracy of peer grading, and these models have achieved good performance in MOOCs. However, our experiments demonstrate that these models fail to deliver accurate inferences in the SPOC scenario because affinity among students may seriously affect the objectivity and reliability of students in the peer-assessment process. To address this problem in SPOCs, this paper proposes a human-machine hybrid peer-grading framework, in which an CNN(Convolutional Neural Networks)-based automated grader works as a filter to ensure reasonable peer scores before Bayesian models are utilized to infer the true scores. This framework can significantly eliminate the severely biased scores of undutiful students and, thus, improve the accuracy of the true-score estimation of the Bayesian peer-grading models. Both the simulated and actual peer-grading datasets in our experiments demonstrate the effectiveness of this new framework for SPOCs.