SUS(Syestem Usability Scale)用来测量系统的可用性，并给出一个用百分制来计算的分数，超过60分被认为是good usability。我自己常使用SUS来测量某个application，某个网站或者设备，系统的可用性，尤其在竞争对手分析(competitive analysis)的时候，SUS的最终数据的差异和实际使用中用户感受到的差异是很一致的。这也说明SUS具有很高的效度。
那怎么使用SUS呢？先看看下边的英文吧，一个印度人写的他是怎么样用SUS的：(如果你用著名的Techsmith Morae的话，你就会知道，SUS是Morae 3里默认的后测量表)
SUS questionnaire (Brooke, Digital Equipment Corporation, 1996)
SUS questionnaire consists of 10 questions that are evaluated using a Likert scale ranging from 1 for ‘Strongly Disagree’ to 5 for ‘Strongly Agree’.
Q1. I think I would like to use this system frequently.
Q2. I found the system unnecessarily complex.
Q3. I thought the system was easy to use.
Q4. I think that I would need the support of a technical person to be able to use this system.
Q5. I found the various functions in this system were well integrated.
Q6. I thought there was too much inconsistency in this system.
Q7. I would imagine that most people would learn to use this system very quickly.
Q8. I found the system very cumbersome to use.
Q9. I felt very confident using the system.
Q10. I need to learn a lot of things before I could get going with this system.
Scoring the SUS
SUS scores have a range of 0 to 100. To calculate the SUS score, first sum the score contributions from each item. Each item’s score contribution will range from 0 to 4. For items 1, 3, 5, 7 and 9 the score contribution is the scale position minus 1, e.g. position 2 will equal ‘2-1’ a score of 1.
For items 2, 4, 6, 8 and 10, the contribution is 5 minus the scale position, e.g. position 2 will equal ‘5-2’ a score of 3.
Multiply the sum of the scores by 2.5 to obtain the overall value of SUS. A score of around 60 and above is generally considered as an indicator of good usability.
SUS has been made freely available for use in usability assessment, and has been used for a variety of research projects and industrial evaluations; the only prerequisite for its use is that any published report should acknowledge the source of the measure.
The method employed to administer the test was to make available the test online. The users were invited to participate in the survey, where they evaluated the questions and rated them as they found appropriate. The survey was administered pre-deployment to measure and benchmark as-is version and then post deployment after the user had the opportunity to use the new system for some time. This enabled the comparison between two versions of the same application. It also provided score to compare between different applications and determine the usability score of a particular application in comparison to others.
Initially it was supposed to be just these 10 questions to gather the score, but it as found that the Product Managers were not comfortable with just the scores as they wanted to know the reason for low/ high scores. Before the introduction of SUS there was no such measure against which the applications were compared, though they did go through a final usability testing. But there was no number to compare different applications and determine how usable the applications were on a scale. Hence there was some resistance initially, and to make the product managers more comfortable three open ended questions were added to the questionnaire. The questions were “What I dislike about the application, what I like about the application, and what I would like to have”. These required user comments, and subjective qualitative data were collected through these questions. While they did provide valuable input, these questions did not form part of the final SUS score which was dependent on the original 10 SUS questions. One important function that these added questions performed was to give insight into what may be wrong with applications that had low SUS score. These also made the Product Managers more comfortable with the score as they could identify with the issues instead of merely being provided with a number.