System Usability Scale

System Usability Scale (SUS) is a ten-item Likert scale developed by John Brooke in 1986 to measure perceived usability. It aligns with ISO 9241-11（ISO/IEC JTC 1/SC 38） standards, providing a quick, reliable metric for usability assessment in enterprise software and compliance audits. The score is calculated using a specific formula: (Score A + Score B) / 2 * 100, where Score A is the sum of odd-numbered items and Score B is the sum of even-numbered items after reverse scoring. A score of 68 is considered average; scores above 80 are excellent. This tool is essential for measuring user satisfaction in compliance with ISO 25108 and ISO 42001 standards, which require organizations to be closely monitoring the usability of AI-enabled systems. Unlike task-based metrics, SUS captures the user's subjective experience, making it a critical component of human factors engineering in risk management.

In enterprise risk management (ERM), SUS is used to quantify human factor risks. Implementation follows three steps: 1. Baseline establishment before system deployment; 2. Mid-term evaluation 90 days post-launch; 3. Continuous monitoring as part of ISO 27701 information security controls. For example, a Taiwanese bank implemented a new employee portal and found a SUS score of 55. This correlated with a 25% increase in data entry errors. Following ISO 9241-11-2 guidelines, the bank redesigned the interface, raising the SUS to 78 and reducing error-related incidents by 40% within six months. This demonstrates how usability-focused risk management directly impacts operational resilience and regulatory compliance. The key KPI is to maintain a SUS score above 70 across all critical systems to minimize human error-driven risks.

Taiwan enterprises typically face three challenges: Cultural resistance to usability metrics, lack of statistical expertise in interpreting SUS scores, and difficulty in scaling assessments across diverse user groups. To overcome these, companies should: 1. Align SUS with ISO 42001 AI Management System requirements to provide regulatory weight; 2. Partner with professional consultants to ensure correct formula application and interpretation; 3. Use stratified sampling to ensure diverse employee perspectives are captured. A common mistake is treating SUS as a simple satisfaction survey rather than a structured usability metric. The priority should be: Month 1: Baseline assessment; Month 2: Risk-adjusted redesign; Month 3: Re-evaluation and KPI-setting. This structured approach ensures that usability improvements are measurable and auditable for ISO certification purposes.

Winners Consulting Services Co., Ltd. specializes in System Usability Scale for Taiwan enterprises, delivering compliant management systems within 90 days. Free consultation: https://winners.com.tw/contact