Shazeeye's Blog Thoughts on User Experience, Technology and Business

27May/110

Usability Metrics: Measuring the user experience

Usability is making a product or website easy to use so that a user can complete his/her goals without getting frustrated. Usability metrics give structure to the design process and inform decision makers. As a usability expert we aim to execute a 'wow' experience by measuring effectiveness (can you complete the task?), efficiency (can you complete it with minimum effort and time?), learnability (how quickly can you learn to do it?) and satisfaction (how happy or satisfied are you with the experience?).

Two people in this field have motivated me- Jeffrey Sauro and Tom Tullis. Jeff wrote an exceptional paper on standardizing usability metrics into a single score. Tom Tullis is a true usability guru with whom I've had the wonderful opportunity to work with at Fidelity Investments. His book 'Measuring the User Experience' is a must read for anyone trying to create a 'wow' user experience. Insights in this post are from his book and my experience. The metrics are defined in detail below.

Efficiency: can be measured through task completion success (successful or not), task completion time, number of clicks to complete tasks, number of page views and comparing user performance  to expert performance

Effectiveness: can be measured through lostness (number of steps a user takes to complete a task relative to minimum number of steps to complete a task), intuitiveness (percentage of items placed in correct menu category using a card sort), awareness (did you notice it? a memory test to repeat what the person noticed or an eye tracking test),  log data checks (live user data is analyzed to study where users fail or are having issues with the task), A/B testing (test 2 design concepts to identify which is more effective), number of issues based on severity and frequency which can also be categorized into user interface parameters such as navigation issues, terminology issues, interaction issues, etc.

Learnability: or the ease of learning a new product/website can be measured by the time it takes someone to be proficient with the product.

Satisfaction and other metrics: self reported metrics (through rating scales, qualitative feedback and online survey tools) on various factors such as satisfaction, ease-of-use, engagement and enjoyment. It could also measure a call to action such as the probability of purchasing the product or recommending it to a friend. Physiological factors such as heart rate changes, eye tracking and sentiment analysis are some other ways to measure the experience.

Tom Tullis has a neat image of when to use each metric or combination of metrics in his book.

Want an easy-to-use metric? The System Usability Scale (SUS) is an easy way to measure the usability of any product/website. Ask users to complete a task or a few critical tasks and give them this questionnaire to rate. You can calculate the SUS Score which could range from 0-100. A score of 80+ is good usability but for a more detailed interpretation read this paper.

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