Better Peer Grading through Bayesian Inference
This work addresses peer grading systems for educational settings, offering incremental improvements over existing probabilistic models.
The paper tackled the problem of aggregating noisy peer grades by extending Bayesian inference methods to account for strategic student behavior, censored data from rubrics, and interpretability through mixed integer programming, showing accurate estimation of true grades and student characteristics in experiments across four large classes.
Peer grading systems aggregate noisy reports from multiple students to approximate a true grade as closely as possible. Most current systems either take the mean or median of reported grades; others aim to estimate students' grading accuracy under a probabilistic model. This paper extends the state of the art in the latter approach in three key ways: (1) recognizing that students can behave strategically (e.g., reporting grades close to the class average without doing the work); (2) appropriately handling censored data that arises from discrete-valued grading rubrics; and (3) using mixed integer programming to improve the interpretability of the grades assigned to students. We show how to make Bayesian inference practical in this model and evaluate our approach on both synthetic and real-world data obtained by using our implemented system in four large classes. These extensive experiments show that grade aggregation using our model accurately estimates true grades, students' likelihood of submitting uninformative grades, and the variation in their inherent grading error; we also characterize our models' robustness.