Patrick Jordan’s book, An Introduction to Usability.
What is Usability?
Usability is a quality that can be measured according to how this approach is applied. Itis the extent to which a product is “user-friendly” through its effectiveness, efficiency, and engenders satisfaction.”
Effectiveness of a product is “the extent to which a goal or task is achieved.” This can be measured by a simple pass or fail or with “error rate.” Error rate can be broken down into four categories:
minor: user can correct the error instantly.
major: user may take more time to correct the error, and start getting annoyed.
fatal: user can not complete the task or achieve the goal.
catastrophic: user can not complete the task or achieve the goal, and other serious problems may result.
Efficiency is the amount of effort it takes for a user to extract information. Less effort equals higher efficiency. For example, if you can complete the task without having to read a manual or google multiple tutorials.
Satisfaction refers to the joy a product brings the user. This level of comfort with a product can be measured using interviews or questionnaires.
Effectiveness and Efficiency may be the most important aspects of usability for work-related products, and Satisfaction may be more of a priority for leisure-related products. Usabilitycan also be thought of as the interaction between the user and the product with regard to the task to be completed.
Other important user characteristics to consider when designing:
Experience–Prior experience with a product can affect how easy/hard it is to complete a task.
Domain Knowledge –“Understanding ability and information that applies to a specific topic, profession or activity.”
Cultural Background – Take into account “population stereotypes” when designing.
Disability – Pay attention to the specific needs of the disabled will open up opportunities that may not have been previously available. Also, designing for outliers can provide benefits for all.
Age & Gender –It is important to take into account the different attitudes each generation has towards technology. This will help inform your design.
Guessability –Must communicate affordances very quickly, so no guessing.
Learnablity – How much a user gets better after using a product for a while. Efficiency will be attained.
Experienced User Performance (EUP)– User not required to learn quickly, but once they gain knowledge they must perform at a high-level.
System Potential - “The optimum level of effectiveness, efficiency, and satisfaction with which it would be possible to complete specified tasks with a product.
Re-Usabilty – Users can achieve a specified task with a particular product after a comparatively long period away from the task.
The lack of usability results in annoyance by the user, can have financial implications affecting product sales and productivity, and may result in safety concerns for user and/or others involved. It is important to use the principles below as a checklist for your design.
The Principles of usable design are:
Consistency –“Design a product so that similar tasks are done in similar ways.”
Compatibility –“Design a product so that its method of operation is compatible with users' expectations.”
Consideration of users resources – Take into account all the senses available (sight, smell,etc.)
Feedback “Design a product so that actions taken by the user are acknowledged and a meaningful indication is given about the results of these actions.”
Error Prevention & Recovery – “Design a product so that the likelihood of user is minimized and so that if errors occur they can be recovered from quickly and easily.”
User Control –“Design a product so that the extent to which the user has control over the actions taken by the product and the state that the product is maximized.”
Visual Clarity –“Design a product so that information displayed can be read quickly and easily without causing confusion.”
Prioritization of Functionality & Information – “Design a product so that the most important functionality and information is easily accessible to the user.”
Appropriate Transfer of Technology – “Design a product so that making appropriate use of technology developed in other contexts to enhance the usability of a product.”
Explicitness –“Designing a product so that affordances are given as to its functionality and method of operation.
A designer should create a usable design through a “user-centered” design process. To start this part of the process a designer should consider:
Specifying User Characteristics both physical and cognitive – such as height, reach, or strength, attitudes users hold, specialist knowledge, and any user expectations.
Requirements Capture– usability requirements such as terminology used, understanding users lifestyle and attitude, and context of product use.
Usability Specifications– such as safety, acceptable quality tolerances, and using focus groups, interviews, and questionnaires to answer specific usability questions.
Iterative Design & Prototyping – “Formulate some product concepts that will evolve through design/evaluation cycle.” Use SWOT analysis to identify weaknesses and strengths, then repeat the process.
Examples of Prototyping:
Product Specification– a simple verbal or written description of the form and functionality of a product.
Visual Prototype –a simple visual representation either paper-based or screen-based of sketches and drawings.
Models – they can be made of cardboard, clay, wood, or foam. (suitable weight may be important for a product).
Screen-based Interactive Prototypes –offer simulated interactions (Invision, Adobe XD, etc.) that are less expensive to make changes to at this stage.
Fully Working Prototype – These 'appear' to be working prototypes to the user, but are actually being manipulated by the investigator.
