What is it and why is it important?
“The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.”
Breaking it down: specified users, context of use, effectiveness, efficiency, satisfaction.
Effectiveness
The accuracy and completeness with which users achieve specified goals.
- Tasks completed
- Ratio of successes to failures
- Objectives achieved
- Errors in a task
- Tasks with errors
- Task error intensity
Example:
- Task 1: Success 100%
- Task 2: Fail 40%, Success 60%
Efficiency
The ability to do a task successfully, without wasting time or energy.
- Total task time
- Cost-effectiveness
- Productive vs unproductive time
- Unnecessary actions
- Fatigue
- How often help is used
Example: Time taken to do
- Task 1: 30 seconds
- Task 2: 60min
- Task 3: 10min
Satisfaction
After they’ve completed the tasks, how do users feel about the experience?
System Usability Scale
1: Strongly disagree
2,3,4: k
5: Strongly agree
- I think that I would like to use this system frequently
- I found the system unnecessarily complex
- I thought the system was easy to use
- I would need support of a technical person to use the system
- I found the functions in this system were well integrated
- I thought there was too much inconsistency in this system
- Most people would learn to use this system very quickly. I found the system very cumbersome to use
- I felt very confident using the system
- I needed to learn many things before starting on the system
Calculating the score
- Add the scores for all odd-numbered questions, then subtract 5 from the total to get (X).
- Add the scores for all even-numbered questions, then subtract that total from 25 to get (Y).
- Add the total scores (X+Y) and multiply by 2.5.