In this article, we will look at the importance of usability scales, such as the System Usability Scale (SUS) , to provide a quantitative dimension to your analyses . We will also discuss the different methods available, adapting the tools according to your targets, and integrating these scales throughout the design cycle of your website.
Illustration representing the usability of a website, showing users easily navigating a clear and intuitive interface.
Methods for evaluating the usability and user experience of an interface
According to ISO 9241-11 (2018), usability is the ability of an interface to be easily used by a person to perform a defined task . On the other hand, user experience is a broader concept, since it represents the quality of the user's experience in digital or physical environments. Usability therefore represents, in a way, the pragmatic aspect of user experience.
To evaluate the usability or user experience of websites and applications, you can use three main types of methods :
inspection methods;
user testing;
satisfaction questionnaires.
In scientific literature, two approaches are distinguished: the analytical approach and the empirical approach.
On the one hand, the analytical approach groups together inspection methods that evaluate the characteristics of the system. The interfaces are studied here according to a set of rules, recommendations and principles, in order to check their conformity to certain criteria and to detect the problems that they may pose. This could be, for example, an ergonomic audit .
On the other hand, the empirical approach includes user testing and satisfaction questionnaires. Empirical evaluations, which require the existence of the real system or a prototype (simulation of the system) and the presence of users , consist of collecting data on the behaviors and perceptions of end users, during or after the use of a system. This empirical evaluation of end user perceptions is most often carried out within the framework of a usability test, which asks the user to manipulate the system for a defined period and may include verbalization techniques out loud. Typically, user perceptions are also collected through scales filled out after usability testing to supplement the information and have quantitative data.
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The case of satisfaction questionnaires: UX scales and usability scales
Satisfaction surveys can be measured through UX scales and gcash database usability scales. Let’s see which options to prioritize and when.
Prefer a psychometric scale
To measure concepts such as usability or user experience in an objective and standardized way, you should favor a psychometric instrument . These scientific tools allow you to evaluate latent concepts, such as individual differences, using measurable indicators.
For example, the assessment of a person's perception of the usability of an interface is evaluated through questionnaires that include specific items, often quantified on a Likert scale . The latter corresponds to a semantic rating system , which is used in surveys to measure and evaluate perceptions, attitudes and opinions. For each statement, the respondent must use the following rating system to answer:
Completely agree;
Rather agree;
Rather disagree;
I don't agree at all.
A psychometric instrument is distinguished by three essential characteristics.
Standardization : This means that the questionnaire is administered to participants under the same conditions and their responses are also analyzed in the same way. Depending on the score obtained, the interpretation will be the same between people, which allows us to know whether a system is perceived as good, excellent, acceptable or bad .
Objectivity of measurement : Here, the results do not depend on subjective assessments. Indeed, different assessors should obtain similar results by administering the same test to the same person.
Psychometric properties : These correspond to the quality of the measurement in terms of precision (reliability, sensitivity and specificity) and validity. A questionnaire is said to be reliable if, used under the same conditions with similar groups or the same group, it produces consistent results. It is considered sensitive and specific if it allows to correctly detect, in a targeted population, the people who perceive poor usability of the system from those who perceive good usability. Finally, it goes without saying, a questionnaire is said to be valid if it correctly measures what it is supposed to measure, here usability or user experience.
Opting for a psychometric scale therefore ensures a reliable and scientifically validated assessment , essential for informed and fair decisions in your professional practice.
Please note, if you wish to evaluate your website or application with a French-speaking population, ensure that the scale is validated in the French version.
