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What is the Usefulness ?

Usability is quality which describes how easy system is to use. In the word of UX, You maybe familiar with Usability Testing methods for testing the usefulness of your digital product. However, is there a way to measure such usefulness ? How do  I translate usefulness into clearly understandable value or categories?

Usability  metrics such as Tast Success Rate ( TSR ), Net Promoter Score (NPS ), and Sytem Usability Scale (SUS )can help you answer this question. However, these metrichave different benchmarks. For example, as the name suggests, the Task Success Rate measure usability based on the many user are likely to recommend your product to others. Meanwhile, the System Usability Scale of 0-100based on a questinnaire filled out by the user. This article will discussSUS further, from how to calculate it to tips that will help you use SUS. Let’s go!

System Usability Scale ?

The System Usabilitry Scale was first created by John Brooke in 1986. To date, SUS has been commonly used to test usefully of various, from software to hardware, keep mind, the value of SUS is not an absolute value of the usefulness of a system, but value which measures the perceived usefulness by the user. The results from SUS can be used to compare the usability of different designs. 

The SUS questinnare consists of 10 statements wich 5 response options. After getting the results of the questionnaire, calculations were made to get the final SUS score. The value in the from og a number on a scale of 0-100 willrepresent the level of usability of the system being tested. However, the scale is not equal to proportion, so ( for example ) 65on SUS is not equal to 65%, but will be more to 41%

Still confused? Keep reading ya, we will discuss one by one !

SUS Questionnaire

The SUS Questionnaire can be administered to the user either after completing each tasks on Usability Testing ( UT ), as well after completing the UT as a whole, taking into account :1. Filling out the questionnaire

Everytime you complete a task describes the user’s thought on the system on the task he just did.2. Filling out the questinnaire after

The UT as a whole reflects the user’s thought on the whole system being tested.

The 10 statement given are :1. I think Iwill Use this system often.2. I fell this system is too complicated.3. I think this system is easy to used.4. I think I will need help from a technical person to able to use this system.5. I find the various funcions of this system well integrated.6. I think this system has alot of in consistencies.7. I image that most people will learn to used this system very quickly.8. I find this system very impractical when used.9. I feel very confident when using system.10. I need to learn a lot of things before I can use this system.

If you look back, you maybe able to see pattern found in the 10 questionnaire statements: statements on odd number are negative.The placement of these intervals will be useful when calculating the SUS value later. 

Then, the five resposes that the user can choose from range from 1 ( stronge disagree )to 5 ( strongly agree ), as shown in the image below :

Calculatin

To calculte the SUS value, there are several rules that you must apply :1. For odd number, the number selected by the user is subtracted by 1. (x-1)2. For an even ststement number,subtract 5 by the number selected by the user. (5-x)3. All values from the results of rules 1 and 2 will range from 0-4 (with the number 4 being the best.)4. Add up all these values and multiply by 2.5. this multiplication will change the scale from 0-40 to 0-100.

Data from different user can be avaraged.

Translate SUS Values

If you have got the value, then what should you do with the value?

How to determine whether the value is good or not? ( Remember, the SUS value is not the same as a 

Jeff Sauro, PhD., founding principal of measuring, conducted research on 500 studies to study SUS. From his research, he stated that the number that become the avarage SUS score was 68. This mean that a system that gets an SUS score above 68 is above the average — and —   be considered feasible  tor acceptable.

Jeff Sauro, then normalized the SUS scale to interpret it into other rating categories, as can be seen in the table below :

SUS NumberMarkAdjectivePercentile
84.1-100A+Best Imaginable96-100
72.6-84.0B-  -AExelent65-95
62.7-72.5C- -C+Good35-64
51.7 – 62.6DOk15-59
25.1 – 51.6FPoor2-14
0-25FWorst Imaginable0-19

For the full version, visit this Jeff Suaro article.

Tips About  SUS 1. Apart from using questinnaires in paper form, SUS can be done with online survey platform such as typeform or Google Form – which – can the calculation of data in spreadsheets.2. If in doubt with your own calculation, you can the SUS calculator from UIUX Trend here.—– 

So, that was the discussion about system Usability Scale. Share and like this article if it’s useful! Thank You!

Reference

Measuring U: Measuring Usability with the System Usability Scale (SUS). by Jeff Sauro

Beyond the NPS: Measuring Perceived Usability with the SUS, NASA – TLX, and the Single Ease Question After Task and Usability Test (nngroup.com). by page Laubheimer

What is Usability Testing? I Interaction Design Foundation  (IXDF) (interaction-design.org).Interaction Design Foundation

SUS Calculator—UIUX Trend UIUX Trend

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