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SUS Topics

Predicting Net Promoter Scores from System Usability Scale Scores

Guest Post By Jim Lewis • January 3, 2012

System Usability Scale (SUS) scores are often collected along with Net Promoter Scores in evaluations of software and website usability. An examination of 81 datasets from 2200 users shows that dividing SUS scores by 10 does a decent job of predicting the Net Promoter Score.[Read More]

Measuring Usefulness

Jeff Sauro • November 1, 2011

A product must be useful and usable to be adopted and both have been shown to predict reported usage. However, perceived usefulness is 1.5 times more important than usability when predicting technology acceptance.[Read More]

How much does the usability test affect perceptions of usability?

Jeff Sauro • May 17, 2011

In measuring perceived usability of five popular websites, a single difficult task will lower post-test usability scores by 8%. This is largely driven by the least experienced users whose scores dropped by almost 20%. A difficult task doesn't appear to affect the most experienced users' attitudes.[Read More]

Are both positive and negative items necessary in questionnaires?

Jeff Sauro • April 26, 2011

There is a long tradition of including items in questionnaires that are phrased both positively and negatively to minimize extreme response and acquiescent biases. An analysis of an all positively worded version of the SUS found little evidence for these biases. This suggests response bias effects are small and outweighed by the real effects of miscoding by researchers and misinterpreting by users.[Read More]

Measuring Usability with the System Usability Scale (SUS)

Jeff Sauro • February 2, 2011

At only 10 items, SUS may be quick to administer and score, but data from over 5000 users and almost 500 different studies suggests that SUS is far from dirty. Its reliability and validity are as high as or higher than commercial questionnaires. Its versatility, brevity and wide-usage means that despite inevitable changes in technology, we can probably count on SUS being around for at least another 25 years.[Read More]

Does prior experience affect perceptions of usability?

Jeff Sauro • January 19, 2011

SUS scores from 1100 users from 62 websites showed that repeat users rate the website as 11% more usable than first time users. SUS scores from 800 users of 16 consumer software products showed that the most experienced users (5+ years of experience) also rate the software as 11% more usable than the least experienced users (less than 3 years of experience).[Read More]

5 Second Usability Tests

Jeff Sauro • November 9, 2010

System Usability Scale (SUS) Scores from users who had only 5 seconds to assess the usability of a website were statistically indistinguishable from users who had no time limit. Users who had only 60 seconds on a website tend to rate websites as more usable than those who had only 5 seconds or no time limit.[Read More]

That's the worst website ever!: Effects of extreme survey items

Jeff Sauro • September 21, 2010

Items in the System Usability Scale (SUS) were rephrased to either all extreme positive or all extreme negative wording and average scores were compared. Users disagree more with items that are worded in the extreme and resulted in significantly different SUS Scores.[Read More]

Can we trust data from professional usability test-takers?

Jeff Sauro • February 9, 2010

In a comparative test, satisfaction scores and completion rates from professional usability test-takers were nearly identical to lab-based users. However, time on task data differed significantly and showed much higher variability. For testing websites intended for a general audience the use of professional testers appears to provide mostly reliable data quickly and for a fraction of the price.[Read More]

Can you use the SUS for websites?

Jeff Sauro • January 18, 2010

The System Usability Scale (SUS) is the most popular standardized usability questionnaire because it's free and short. It was designed over 20 years ago before the web existed. Should it be used on websites?[Read More]

Does better usability increase customer loyalty?

Jeff Sauro • January 7, 2010

I examined the relationship between customer loyalty as measured by the Net Promoter Score (NPS) and System Usability Scale (SUS) questionnaire from several usability tests. I found that perceptions of usability account for about 1/3 of the changes in customer loyalty. Increasing your usability will lead to increased loyalty.[Read More]