‑ Usability Goals
There are certain system qualities when it comes to products and services and usability, which is a big part of the user experience, is one of them. The usability quality can be divided into sub-qualities. There is no complete list of different usability qualities, but there are some recommendations and definitions that names a few, such as the list of design principles or the ISO definition:
ISO 9421-11 Usability definition
The effectiveness, efficiency and satisfaction with which specified users achieve specified goals in particular environments.
The sub-qualities in the definition are effectiveness (task completion), efficiency (task in time) and satisfaction (the user’s experience).
Any adjective that users may use to describe their interaction with the system is a subquality to usability. If the user wants the system to be snappy, then a corresponding usability quality might be quickness or swiftness. Other words to listen for might be polite, simple, consistent, fun, flexible, pleasant, adaptive or familiar.
The best way of actually using these adjectives in your design and evaluation processes are to convert them to usability goals. A usability goal is a more generic but also specific definition of the quality or adjective, and it is usually accompanied by measurable objectives. Consider this example by Hackos & Redish1:
Users (i.e. medical doctors) want to be sure they can get all to all the patient information they need with ease so that they can make good diagnoses.
Users are satisfied that the patient information is easy to access and that it is organized so that it doesn’t interfere with the patient’s treatment.
If we make them measurable, they can be what makes your usability process legitimate in a world of non-believers. You can for instance measure efficiency by the time it takes to complete a task, by judging the percentage of the task that was completed or the number of times the interface misleads the user. What works best is up to you. Below is another example from Hackos & Redish1, this time of how a usability goal can be translated into a measurable objective.
Users will find the installation process understandable and easily follow it step-by-step to achieve a successful installation.
No more than 10% of the users will call customer support for help to install the product
As you can see, a usability goal is something describing a beneficial behavior or important need, and can thus be used as design principles and motivation, and the measurable objective is what you need for evaluation.
1 - Hackos, J.T. & Redish, J.C. (1998). User and Task Analysis for Interface Design. New York: Wiley & Sons.