Which metric is commonly used to measure usability success after launch?

• A. Task success rate
• B. Customer churn rate
• C. Conversion rate
• D. Page load time

Answer: (A)

Measuring usability success after launch centers on whether users can complete the tasks you designed the product for. Task success rate is the best fit because it directly shows the percentage of tasks that users finish correctly, giving a clear signal of how usable the interface is in real use. When this rate is high, it means users can accomplish their goals with little friction; when it’s low, you have actionable insight into where the design needs adjustments. You can gather this through real-world analytics or usability studies by defining representative tasks and checking if users complete them as intended. Other metrics are useful in their own right but don’t directly measure task completion: churn rate looks at whether people stop using the product, conversion rate tracks a business goal that can be influenced by many factors beyond usability, and page load time affects perceived performance but isn’t a direct measure of task success.