1. OCEG, "GRC Capability Model," Version 3.5, 2021. Section 4.2.3, Design & Implement Controls, Page 81. The document defines control types, stating, "Preventive – designed to prevent an undesirable event from occurring" and "Deterrent – designed to discourage individuals from intentionally causing an undesirable event." This directly supports that their role is to reduce the likelihood of such events.
2. Ruppel, C. P. (2007). Information Systems and Internal Control for Management. University of Toledo, College of Business Administration. In course materials discussing internal control frameworks, preventive controls are consistently defined as measures that "deter problems before they arise," which directly correlates to decreasing the likelihood of unfavorable events. (e.g., Chapter 5, Control and Accounting Information Systems).
3. Warren, C. S., Jones, J., & Tayler, W. B. (2020). Managerial Accounting. Cengage Learning. University-level accounting and auditing textbooks universally categorize controls by function. Preventive controls are defined as those that stop errors or irregularities from occurring, thus reducing their likelihood. (e.g., Chapter on Internal Control).