Everyone wants his product or feature to fit user’s needs. Hence many approaches are done to reach this goal, as for example, by doing User Interviews, Focus Group Discussion, Usability Testing, and other methods. Questions that might arise after executing these methods are:
Does the product resolve the user’s problem? How efficient does it work? Are users satisfied with this product?
Have you ever done a user interview to find a good response but then got confused on which parameter to attest if the product or feature fits its purpose?
How to use NPS and SUS Score?
Net Promoter Score (NPS) how-tos are easier to be found on the internet. Here I will talk about its less-known rival: System Usability Scale (SUS).
What is the System Usability Scale (SUS)?
System Usability Scale (SUS) is a questionnaire to measure usability perception. It was found by John Brooke in 1986 and used to test the office electronic system back then.
How to apply it?
System Usability Scale (SUS) contains 10 questions where participants are given 1–5 scale to fill, according to how they agree with every statement regarding product or feature on the test. 1 means strongly disagree while 5 means they strongly agree with the statement.
Here are 10 questions in SUS that can be customized for your product or feature:
- I think that I would like to use this feature frequently.
- I found the feature unnecessarily complex.
- I thought the feature was easy to use.
- I think that I would need the support of a technical person to be able to use this feature.
- I found the various functions in this feature were well integrated.
- I thought there was too much inconsistency in this feature.
- I would imagine that most people would learn to use this feature very quickly.
- I found the feature very cumbersome to use.
- I felt very confident using the feature.
- I needed to learn a lot of things before I could get going with this feature.
How to calculate?
· For every odd-numbered question, subtract 1 from the score (X-1)
Example: In question number 1. I think I will frequently use this feature, the participant responded with score 4. The formula is X-1. X is the score given by the participant. Therefore the calculation would be 4 subtracted by 1. The final score from the participant for statement number 1 is 3.
· For every even-numbered question, subtract the score from 5 (5-X)
Example: In question number 2. I think this feature is too complicated while it can be simplified, the participant responded with score 1. The formula is 5-X. X is the score given by the participant. Therefore the calculation would be 5 subtracted by 1. The final score from the participant for statement number 2 is 4.
· Sum the scores from even and odd-numbered questions. Then multiply the total with 2.5
After you calculate every odd and even numbered statement, your next job is to sum all scores. Note that the highest score for each question is 4 and 0 is the lowest. After summing scores from all 10 questions, the next step is multiplying the total with 2.5 and that would be the final SUS Score for your product or feature. The highest SUS Score is 100. If you get more than that, consider rechecking your calculation.
This example might help you to fully comprehend. Calculation values for each odd-numbered questions are 4, 2, 3, 4 and 3 respectively so that the accumulation of odd-numbered questions is 4+2+3+4+3 = 16. Meanwhile, the calculated values for even-numbered questions are 3, 3, 4, 2 and 3 which makes the total accumulation of even-numbered questions to be 3+3+4+2+3 = 15.
Then sum all scores of odd and even numbered questions. From this data, we got 16 (odd) + 15 (even) = 31. If we multiply the sum result with 2.5, it would be 31 x 2.5 = 77.5. The System Usability Scale (SUS) Score of this example is 77.5.
We might not find the specific problem of your product or feature with this SUS Score, but this can be a base to see your product or feature’s usability.
Your next question is probably what is the minimum SUS Score for a product or feature to be categorized as good?
From some references I have read, the standard average of SUS score is 68. If your product or feature reaches less than that, you might have to go the extra mile to change or improve your product or feature usability.
Below is a general guideline on SUS Score interpretation:
To make it easy for you to learn more about System Usability Scale (SUS), I have attached a System Usability Scale (SUS) calculation template along with Net Promoter Score (NPS) I frequently use. You can download it here.
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