A seamless user experience is vital to the success of any business. In fact, 70% of online businesses fail because of bad usability – to understand how well a product meets users’ needs and expectations; businesses must first understand how users interact with the product. But how do you measure usability? Below, you’ll find six of the most effective usability metrics and details on how to measure them.
Top Usability Metrics You Need to Track
There are many usability metrics that you could be tracking, like time on task, task success rate, ease-of-use rating, etc. Usually, these metrics focus on the ease of task or event completion by users, and they broadly fall into three categories – Effectiveness, Efficiency, and Satisfaction.
So, where do you start? Well, here are six key usability metrics to consider, and we have divided them into the three types mentioned above.
Usability Metrics for Effectiveness
#1 Task Completion Time
To measure the usability of a product, researchers often ask users to complete a few simple tasks while they observe and record the experience. Task completion time measures the total task duration. With it, you can record users’ task completion time (basically how long a user takes to complete a task in seconds or minutes).
It’s fair to assume that if a task takes too much time, the experience needs improvement, as good usability usually means that users can perform their tasks quickly and successfully.
When you observe that the time spent on a task is long, it’s crucial to identify the reason behind it – is it because the user journey is confusing, or are there UI elements in there misleading the user?
If it is either of the above points, you need to re-look at the user interface from the users’ point of view. Task completion time is a vital metric, and all product teams must measure it because there is a strong correlation between task completion time and user satisfaction levels. Also, the lesser time users spend on a task, the better the user experience.
How to Calculate Task Completion Time
Let’s show you how to calculate task completion time. Suppose you are a website designer and want to find out how easily users can add a particular product to the cart. You can take a sample of 7 to 10 users and ask them to do the task.
During the task, calculate the time taken by each participant to complete it and divide the time by the number of participants. This way, you can find the average time to complete a particular task.
Suppose the average time to find the add-to-cart button is higher than expected. In that case, you should relook at your button’s appearance and placement to make it stand out better. This is critical as unintuitive cart designs often lead to cart abandonments. And just so you know how important this is – The Average Cart Abandonment Rate Across All Industries is around 70%!
#2 User Error Rate
This usability metric helps designers record any mistake or omission a user makes while attempting a task. For example, assume a scenario where users have to buy products from your website. To find the errors, you can create the actual scenario the users must go through to buy a product on your site. Then allow the users to conduct the task and check out successfully.
Observe how they complete the checkout and note any mistakes they make during the process.
If the users make many mistakes while completing the task, it indicates a below-average user experience. And this reduces user satisfaction and prevents users from returning to the application.
How to Compute User Error Rate
You can calculate user error rate in different ways. But the most common type of measurement is the error occurrence rate. Here is how to calculate it:
Total number of errors occurred for all users/ Total number of possible errors for all users
Remember, errors can occur more than once per user per task. To measure multiple errors or multiple possible errors per task, you can calculate the error rate by dividing the number of errors by the total number of attempts.
Usability Metrics for Efficiency
#3 The Overall Relative Efficiency
This metric measures users who successfully completed a particular task with the total time taken by all the users.
How to Calculate the Overall Relative Efficiency:
#4 Time-Based Efficiency
This metric measures the time spent by the users to complete the task and is useful when looking for usability problems as it combines task time and success score.
How to Calculate Time-Based Efficiency
Usability Metrics for Satisfaction
#5 Task Level Satisfaction
This usability metric allows you to get feedback from the users on the usability of your website, app, or product, whether they have successfully achieved the tasks or not.
As is obvious, if satisfaction is low for any task, then that task needs improvement.
The task level satisfaction metric is crucial as it identifies problem points, allowing developers to adjust and improve user experience and satisfaction.
How to Measure Task Level Satisfaction
Once the user finishes the tasks, you can ask a few questions to measure and quantify how easy or difficult it was to complete them. Generally, task level satisfaction is done at the end of the usability test rather than after each task. This helps you measure the overall ease of use from the user’s perspective.
#6 Post Task Satisfaction
Post-task satisfaction is measured after users have finished the task. It doesn’t matter whether they complete it successfully or not. Normally, they are given a questionnaire to measure their task difficulty experience. Generally, these questionnaires contain 3 to 5 questions.
How to Measure Post Task Satisfaction
You can use a questionnaire to quantify and measure how easy or difficult it was to complete a task. There are many types of questionnaires, but some of the most popular ones are:
- ASQ: After-Scenario Questionnaire (3 questions).
- NASA-TLX: NASA’s task load index (5 questions).
- SMEQ: Subjective Mental Effort Questionnaire (1 question).
- UME: Usability Magnitude Estimation (1 question).
- SEQ: Single Ease Question (1 question).
Keep a Pulse on Your Usability Metrics
Satisfied users drive business. And although C-suite knows the importance of user experience, it often gets side-tracked as resources get channeled into other departments.
But as we wrestle with a global recession, optimizing the user experience has become more vital than ever before, as optimizing the user experience can increase conversions.
Tracking the usability of your website or app with metrics allows you to understand the experience you are providing to your users clearly and helps you improve it over time. And usability testing tools like Affect UX can help you do that.
With Affect UX, you can measure your usability metrics and convert them into actionable results, which allows you to instantly act on them.
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