System Usability Scale

How the System Usability Scale Works

The System Usability Scale (SUS) is a versatile and efficient method for assessing the usability of various products, including websites, software, mobile applications, and even hardware devices. It provides a standardized way to collect user feedback and quantify their experience.

Here's how it works:

• Users answer 10 questions after interacting with a system
• Questions alternate between positive and negative statements
• Responses are given on a 5-point scale from "Strongly Disagree" to "Strongly Agree"
• Scores are calculated and normalized to produce a single number between 0 and 100

Benefits of Using the System Usability Scale

1. Quick and Easy: The SUS can be administered quickly, typically taking less than 10 minutes to complete.
2. Reliable: Despite its simplicity, the SUS has been proven to be a reliable indicator of usability across various contexts.
3. Versatile: It can be used to evaluate almost any kind of user interface or product.
4. Benchmarking: The standardized score allows for easy comparison between different products or versions.
5. Cost-effective: As a questionnaire-based tool, it's relatively inexpensive to implement compared to other usability testing methods.

Interpreting SUS Scores

Understanding SUS scores is crucial for making informed decisions about your product's usability:

• Scores below 68 are considered below average
• A score of 68 is considered average
• Scores between 68 and 80.3 are good
• Scores above 80.3 are excellent

It's important to note that these are general guidelines, and the context of your specific product and industry should be considered when interpreting results.

Frequently Asked Questions

• Question 1: How many participants do I need for a SUS evaluation? Answer: While there's no fixed number, research suggests that 5-8 participants can provide reliable results for most studies.

• Question 2: Can I modify the SUS questions? Answer: It's generally recommended to use the standard questions to maintain reliability and allow for benchmarking. However, minor wording changes to fit your context are acceptable.

• Question 3: How often should I conduct a SUS evaluation? Answer: It's beneficial to use SUS throughout the development process, from early prototypes to post-launch, to track usability improvements over time.

• Question 4: Is SUS suitable for all types of products? Answer: While SUS is versatile, it may not be ideal for highly specialized or complex systems. In such cases, it's often used in combination with other usability testing methods.