Do performance trends suggest wide-spread collaborative cheating on asynchronous exams?

Using a data set from 29,492 asynchronous exams in an oncampus proctored computer-based testing facility (CBTF), we observed correlations between when a student chooses to take their exam within the exam period and their score on the exam. Somewhat surprisingly, instead of increasing throughout the exam period, which might be indicative of widespread collaborative cheating, we find that exam scores decrease throughout the exam period. While this could be attributed to weaker students putting off exams, this effect holds even when accounting for student ability as measured by a synchronous exam taken during the same semester. This suggests that precautions can be taken by a CBTF to maintain cheating at a low level (e.g., the level of proctored synchronous exams), in spite of the fact that students are taking their exams over a multi-day period.