Glossary
Time on task
What is time on task?
Time on task measures how long a user spends performing a specified task. In usability testing, it helps assess efficiency alongside whether the user succeeds.
How to measure it
Define when timing starts and ends, and how failures, assistance, and interruptions are handled. Keep those rules consistent when comparing versions or user groups.
Task times are often right-skewed: many users finish relatively quickly, while a few take much longer. A median or geometric mean can describe a typical completion time. An arithmetic mean is useful for average time cost. Choose the measure that answers the question.
Long times can reveal where people got stuck. Do not discard them merely because they are inconvenient for the average.
Example
Suppose median checkout time falls from 4 minutes 30 seconds to 2 minutes 15 seconds after a redesign. That hypothetical result halves the typical completion time. The team should also check completion and the spread of times. A shorter time among successful users could hide the fact that more people abandoned the process.
Why it matters
Faster is useful when people still accomplish what they came to do. Read time on task alongside task success rate, errors, and the testing conditions.