What is task completion rate in UX research?
Task completion rate measures the percentage of participants in a usability study who successfully complete a defined task. It is calculated by dividing the number of participants who completed the task by the total number who attempted it. A task completion rate of 80% means 8 out of 10 participants successfully completed the task without needing to give up or receive assistance. It is one of the most direct behavioral measures of usability because it measures what users can actually do, rather than what they report about their experience.
How is task completion rate used in usability research?
Task completion rates from usability testing provide evidence for design decisions by showing which tasks users can accomplish successfully and which they cannot. A task completion rate below 70-75% typically indicates significant usability problems requiring design attention. Benchmark studies track task completion rates over multiple rounds of testing to measure whether design improvements are increasing users' ability to accomplish key tasks.
What are the limitations of task completion rate?
Task completion rate measures whether users completed a task, but not how difficult or frustrating the experience was. A user who completes a task after significant struggle counts the same as a user who completed it effortlessly. Time on task and error rate provide complementary measures of completion quality. Task completion rate also depends heavily on how tasks are defined: tasks that are too specific may be too easy, while tasks that are too broad may yield ambiguous data.