Understanding user experience (UX) metrics is crucial for businesses to create products that truly resonate with their audience. UX metrics provide valuable insights into user behavior, satisfaction, and overall performance of digital interfaces. By measuring and analyzing these key indicators, companies can make data-driven decisions to enhance their products and services, ultimately leading to improved user retention and business success.
This article delves into 12 essential UX metrics that play a vital role in assessing and optimizing user experience. From task success rate and time on task to error rate and conversion rate, we'll explore how these metrics can be calculated and applied to gain a deeper understanding of user interactions. Additionally, we'll examine more comprehensive measures like the System Usability Scale (SUS) and Net Promoter Score (NPS), which offer broader perspectives on user satisfaction and loyalty. By mastering these UX analytics, businesses can fine-tune their digital offerings and create more engaging, user-friendly experiences.
Task Success Rate Definition
Task success rate, also known as task completion rate, is a binary metric that measures the percentage of users who can successfully complete a given task within a study or test scenario. It is one of the most commonly used performance metrics in user experience (UX) evaluation, reflecting how effectively users can accomplish specific goals or objectives. 1
Task Success Rate Calculation
To calculate the task success rate, the number of completed tasks is divided by the total number of assigned tasks and multiplied by 100. The formula is:
Task Success Rate = (Number of Completed Tasks / Total Number of Assigned Tasks) x 100
The task success rate can be calculated per user or for an entire study. For example, if a participant completes 10 out of 10 tasks, their individual task success rate would be 100%. However, if 8 out of 10 users complete only 3 out of 10 tasks, while the remaining 2 users have a perfect score, the overall task success rate for the study would be 44%.
Task Success Rate Importance
A high task success rate indicates that users can navigate and interact with the product intuitively, meeting its primary objectives. This metric allows businesses to validate whether their software or digital interface is achieving its intended purpose and providing a seamless user experience.
It is crucial to clearly define what constitutes a successful task completion before collecting data. While the task success rate does not provide insights into the reasons for failure, it serves as a useful statistic for assessing overall usability and identifying areas for improvement.
Additionally, tracking the task success rate for first-time users and monitoring its progress over time can provide valuable information about the product's learnability, another key indicator of user experience success. A consistently high task success rate suggests an intuitive and user-friendly interface, contributing to better user retention and a competitive advantage in the market.
Time on Task Definition
Time on task measures the duration users take to complete a given task. Users taking too long to complete a task might indicate they can't find what they're looking for or are lost trying to complete the task.
Time on Task Calculation
There are at least three common ways to report task time:
1. Time to Complete: Time of participants who meet the success criteria.
2. Time on Task: Time of all participants.
3. Time Till Failure: Time of participants who fail to meet the success criteria.
Due to the positive skew of task time data (you can't have less than 0 seconds but there's no theoretical upper limit), it is recommended to report either the geometric mean or the median, depending on the sample size.
Time on Task Importance
Time on task is not a metric that should be reviewed on its own. It needs to be contextualized, and you need to try to understand why it's taking so long for users to complete a task. The goal is to know if users are taking longer than expected because of the design, copy, instructions, or information architecture.
Tracking time on task for first-time users and monitoring its progress over time can provide valuable information about the product's learnability. However, not all users will complete a task "quickly" due to different factors like motor abilities and reading comprehension skills. 5
Time on task should be paired with other metrics like task success rate and user surveys to gage the overall efficiency and ease of use. If the speed of task completion is crucial (e.g., to save a life or avoid a risk), then time on task becomes an important metric in isolation. Otherwise, it may be an unimportant metric if the task requires a more meditative cognitive process. 5
Error Rate Definition
The user error rate measures how many mistakes a user makes when completing a certain task. 6 It is an indicator of usability - if the error rate is high, the design likely isn't as user-friendly as it could be. 6
Error Rate Calculation
There are two ways to calculate the user error rate:
1. Average Error Occurrence Rate: Suitable if the task involves only one potential error opportunity or if tracking a specific error. Calculate by dividing the total number of user errors (across all users) by the total number of possible errors for all users. Multiply by 100 for a percentage. 6
2. Error Rate: Suitable if there are several potential errors per task and measuring the general error rate across the task. Calculate by dividing the total number of errors made (across all users) by the total number of task attempts (number of users x number of potential errors). Multiply by 100 for a percentage. 6
Error Rate Importance
Errors have been shown to correlate with other usability metrics like task time, completion rates, and task-level satisfaction. Errors are often the reason behind longer task times, failed tasks, and lower satisfaction ratings. 7
Unlike task completion rates, errors can occur more than once per user per task, complicating the analysis as a proportion cannot be easily computed. 7 Treating errors as binary data (1 for at least 1 error, 0 for no errors) is the simplest approach, though it loses some information. 7\
An alternative is converting errors into a proportion based on the opportunity for errors, borrowed from Six Sigma's opportunity for defects. This involves identifying places in an interface where users can make mistakes and dividing the total errors by the total opportunities. 7 This retains all error information.
A high error rate indicates potential user pain points that need investigation and design rethinking. 6 Use this KPI as a sign to further enhance usability. 6
Definition The conversion rate is the percentage of users who take a desired action. The archetypical example of conversion rate is the percentage of website visitors who buy something on the site. 8
Conversion Rate Calculation
Conversion rate can be calculated by taking the total number of users who have completed an action and dividing it by the overall size of the audience exposed to that ad, then multiplying that by 100. For example, an advertiser runs a campaign with an audience of 20,000 people. Out of that group, 800 people clicked on the ad (i.e. converted). To calculate this example, divide 800 by 20,000 to get 0.04, or a 4% conversion rate. 9
There is room to tighten the definition somewhat: How do we count the baseline number of "users"? Only as unique visitors, or do we count a person for as many times as they visit during the measurement period? Either way of counting is appropriate, as long as you're consistent and count the same way during all measurement periods. 8
How do we count users who take "desired actions"? That is, how do we count the conversion events? The same two options present themselves: count a specific person only once, no matter whether they buy once or several times during the period. Or count each person as many times as they buy. It seems most appropriate to follow the same rule as determined for counting the baseline number of visitors, but again either rule will work as long as you apply it consistently. 8
Conversion Rate Importance
Of course, you want to track the absolute number of whatever user actions you value. But for the sake of managing your user-interface design and tracking the effectiveness of your UX efforts over time, the conversion rate is usually more important than the conversion count. 8
Even while keeping the design absolutely unchanged, the conversion count could explode if you run a strong advertising campaign that makes a lot of people interested in your product. The conversion rate measures what happens once people are at your website. Thus it's greatly impacted by the design and it's a key parameter to track for assessing whether your UX strategy is working. 8
Successful conversion-focused UX boils down to exceptional clarity in both navigation and messaging, and thorough testing. Design, layout and functionality all contribute toward convincing users to convert. The bottom line is that you need to use UX data and practices to optimize your site for more conversions. Reduce your website's friction points, streamline the buying process and watch your conversion rate increase.
SUS Definition
Created by John Brooke in 1986, the System Usability Scale (SUS) is a widely used tool for evaluating the usability of software, websites, and other interactive systems. 1 SUS is a questionnaire-based instrument designed to measure the perceived usability of a system. It consists of ten statements related to a user's experience with a particular product, along with a five-point Likert scale.
SUS Calculation
To calculate the SUS score for each respondent, follow this formula: for odd-numbered statements, subtract 1 from the user's response, and for even-numbered statements, subtract the response from 5. The SUS score calculation involves steps like data collection, questionnaire, score conversion, summation, and normalization.
A SUS score can range from 0 to 100, with higher scores indicating better usability. Typically, a score above 70 is considered good, while a score above 85 is excellent.
SUS Importance
The SUS is undoubtedly the most frequently used questionnaire to measure usability due to its quick, cheap, tested, and reliable nature. 11 Although simple, it has been validated with thousands of surveys over hundreds of studies for decades, providing intuitive and solid results. 11
NPS Definition
NPS stands for Net Promoter Score, a common metric used in customer experience programs. It measures customer loyalty by looking at their likelihood of recommending a given business. The NPS score ranges from -100 to +100, with a higher score being desirable.
NPS® is often considered the gold standard customer experience metric. Developed in 2003 by Bain and Company, it's now used by millions of businesses to measure and track how they're perceived by their customers. NPS scores provide a snapshot of the overall customer experience; if customers are more likely to recommend a business, it naturally points to a high level of customer satisfaction and a positive customer journey.
NPS Calculation
The NPS score is calculated by asking respondents to rate on a scale of 0-10 the likelihood of recommending a website, product, or service to a friend or relative. The responses are then grouped into three categories:
1. Promoters: Responses of 9 or 10, indicating high satisfaction and strong likelihood of recommendation.
2. Detractors: Responses from 0 to 6, indicating dissatisfaction and likely criticism.
3. Passives: Responses of 7 or 8, indicating moderate satisfaction but low likelihood of recommendation.
The NPS score is calculated by subtracting the percentage of detractors from the percentage of promoters. For example, if 10% are detractors, 20% are passives, and 70% are promoters, the NPS score would be 70 - 10 = 60.
NPS Importance
Frederick F. Reichheld, the author of "The Loyalty Effect," introduced the NPS concept in the Harvard Business Review in 2003. He found that the question associated with NPS best predicted customer behavior and strongly correlated with company growth over time. Reichheld argued that NPS is relevant because customer recommendations and word-of-mouth referrals directly drive revenue growth in many businesses.
A good NPS score indicates a loyal customer base, arguably a company's greatest marketing asset. Bain & Company suggests the following scoring framework: above 0 is good, above 20 is favorable, above 50 is excellent, and above 80 is world-class.
Definition
Accessibility is the concept of whether a product or service can be used by everyone—however they encounter it. 12 It refers to designing and developing websites, apps, and other digital products and services that are usable by everyone, regardless of their abilities or disabilities. 12 Good accessibility means that people can access and use the content and functionality of a website or app in a similar amount of time and effort as someone who does not have a disability. 12 It also means that people are empowered, independent, and not frustrated by something that is poorly designed or implemented. 12
Accessibility in digital/web design simply means designing to make content usable for people with disabilities. 13 Working with accessibility in mind involves designing websites, applications, and digital interfaces that can be navigated by individuals with visual, hearing, motor, or cognitive impairments. 13 Accessibility and inclusivity in design is about making products and services that work for everyone, regardless of their background or circumstance. 14
Accessibility Measurement
The Web Content Accessibility Guidelines (WCAG 2.1) is an internationally recognized set of recommendations for improving web accessibility. 15 All digital interfaces must meet the AA level standards, and some are required to reach the level AAA. 15 The WCAG 2.1 principles are grounded in the notion that a user interface must be perceivable, operable, understandable, and robust at all times. 15
There are four methods for conducting accessibility evaluation: 15
Automated evaluation: Tools that help streamline the evaluation process and highlight major structural problems.
Manual evaluation: Manually checking and rating the interface against a list of standards and providing recommendations for improvement.
Usability testing: Watching people with impaired abilities using your interface and getting feedback on the challenges they face.
Assistive technology testing: Evaluating the process and potential challenges of using assistive technologies to navigate the interface.
Accessibility Importance
Accessibility is important for a number of reasons, including improved usability, reaching a broader user base, enhancing the user experience, promoting equal rights and inclusion, and meeting legal and ethical requirements. 13
Accessibility features that help people with disabilities often benefit other people too. 12 It aligns closely with usability, focusing on simplifying layouts, optimizing code, and making content more understandable and navigable, especially for screen-reader users. 12 Accessibility goes beyond usability, emphasizing the need for content to be usable and accessible to all, promoting equality and inclusion on the web. 12
When your platform is accessible, it increases your user base, as people from different backgrounds and situations can use your product. 13 This expands the reach and customer base of your product. Incorporating accessibility in your designs will enhance the experience of your users (disabled or not), making it easier to interact with your platform. 13
Accessibility promotes inclusivity and prevents discrimination based on disabilities. 13 Everyone deserves to have equal access to opportunities, information, and social services. Legally and ethically, accessibility is a requirement for different domains and platforms. 13 Adhering to these legal requirements ensures compliance and helps avoid potential legal issues. 13
Conclusion
Understanding and applying these 12 essential UX metrics can significantly enhance the user experience of digital products. By measuring task success rates, time on task, error rates, conversion rates, and using tools like SUS and NPS, businesses can gain valuable insights into how users interact with their interfaces. These metrics provide a solid foundation to make data-driven decisions, leading to more intuitive and user-friendly designs.
Ultimately, the goal is to create digital experiences that not only meet user needs but also delight them. By consistently tracking and improving these metrics, companies can build products that users love and keep coming back to. To stay ahead in today's competitive digital landscape, it's crucial to prioritize user experience and continuously refine your approach. If you're looking to level up your UX game, check out how you can create an effective user-friendly ecommerce storefront in 2024.