What is the acceptable success score for user testing?

Based on research, a SUS score above 68 would be considered above average, and anything below 68 is below average.

1. What is a good task success rate?
2. What is a good sample size for user testing?
3. How do you measure success of usability testing?
4. What's the bare minimum number of users needed to run a successful design test?

What is a good task success rate?

78% is an average completion rate

So this is one threshold of good and bad–with anything above a 78% being above average. If you're scratching your head looking for a benchmark for a task, using 78% would be a good place to start.

What is a good sample size for user testing?

In summary, research suggests that from three to twenty participants can provide valid results, and a good baseline is between five and ten participants. In general, there should be more participants for more complex, highly critical projects; while fewer participants are necessary when testing more novel designs.

How do you measure success of usability testing?

To report levels of success, you simply report the percentage of users who were at a given level. So, for example, if out of 100 users, 35 completed the task with a minor issue, you would say that 35% of your users were able to complete the task with a minor issue.

What's the bare minimum number of users needed to run a successful design test?

Before you move into testing, you'll need users. Aim to grab 5–10 users at a bare-minimum per round of testing, but don't go overboard as you'll more than likely be testing over multiple rounds.