User-Centered Design / 7.2 /
Usability
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Usability is about how easy it is to use a product or system. A design team should be “user” driven and frequent contact with potential users is essential. To understand how a product, service or system may be used, the designer must consider the prior knowledge and experience of the users, as well as their typical psychological responses. Evaluation methods that utilize appropriate testing and trialling strategies must be used to determine these aspects.
7.2.1 | Usability objectives
7.2.1 | Usability objectives
Usability is the extent to which a product can be used by its intended users to achieve specified goals effectively (completely and accurately) and efficiently (fast and with minimum effort) while functioning in a predictable and consistent manner. If so, the product can be considered intuitive, pleasant, satisfying to use and tolerant of user errors (that is, it prevents and enables users to recover from errors).
Usability objectives include:
Usefulness - The extent to which a product enables the user to achieve their goals.
Effectiveness - A measure of the speed of performance or error rate and its relation to the capabilities of a product.
Learnability - how easy it is to learn to use a product or how intuitive a product is to use - The extent to which a user can operate a product or system at a defined level of competence after a pre-determined period of training.
Attitude (likeability): The perceptions, feelings and opinions about a product by a user.
7.2.2 | Enhanced Usability
7.2.2 | Enhanced Usability
Enhanced usability increases product acceptance, user experience, and productivity while decreasing user error and required training and support.
Decrease
User Error - Mistakes and slips when using the product due to aspects such as complexity or inefficiency.
Training and Support - Help and guidance such as tutorials or instructions on how to use the product.
Increase
Product acceptance - The knowledge that a product or service paid for will meet up to its defined expectations.
Productivity - Developing products and services with the user in mind so that they can reduce time wasting and simplify complex aspects of the product.
7.2.3 | Characteristics of good user-product interfaces
7.2.3 | Characteristics of good user-product interfaces
The interface of a product is formed by those parts that users of the product interact with. This interaction can happen with any of the users' senses, but most the most common sense for interaction is tactile (touch).
A ‘badly designed’ user interface makes users require constant assistance or significant training. It might also lead to frequent errors in the use of a product. A common cause of bad user-product interfaces results from the addition of functionality to a product, without re-imagining the interface from scratch.
It can be difficult for a designer to distance themselves from the product and look at it through the eyes of a prospective user. This is one of the reasons why user input in the design process is important.
Users (in the broadest sense of the word) can help test the characteristics of a good user-product interface such as simplicity, ease of use, intuitive logic, organization, low memory burden, visibility, feedback, affordance, mapping and constraints.
Visceral design is design that has these characteristics. It speaks to people's nature in terms of how they expect products and systems to function and how they expect to interact with them.
Ease of use and simplicity are requirements of almost any design. They are poorly defined concepts though. In general ease of use is a user sentiment that is determined by better-defined concepts such as affordance, low memory burden and logical mapping.
Simplicity can relate to
A reduction of the number of options for the user to choose from at any given point of the interaction (e.g. the number of buttons)
A reduction of the number of steps needed to perform basic functions.
Making buttons or operations multifunctional.
Making sure the product does one thing well.
Designing a product to be intuitive, logical, and organised will allow new operators to quickly become competent in the basic functions of the product and increase the productivity and efficiency of the product use. Again these concepts do not have clear commonly shared definitions.
What makes a product interface easy to use or intuitive strongly depends on the following characteristics:
Affordance - How well an element on an interface indicates how it is to be used. Buttons afford pushing, knobs afford turning, your hand holds the railing.
Mapping - The correspondence between the (physical) layout or orientation of controls and the consequence of their action.
Low memory burden - Not having to remember how a task is achieved with a product. Features are intuitively accessed with a limited amount of (thinking) steps. The user is guided through the use of the product by the way it is designed.
Visibility - Controls should be easily accessible to the human eye.
Feedback - The provision of information as a result of an action. This can be an audio, visual or aesthetic response. E.g. the clicking of a button when pressed.
Constraints - Limitations on how the product can be used. This can prevent or even correct erroneous use, limit damage.
7.2.4 | Population stereotypes
7.2.4 | Population stereotypes
A population stereotype defines generalizations about the perceptual, cognitive, or physical characteristics of a group of users, such as a cultural group, that are relevant to the design of systems or products for that group. When a person is categorized into a group (population) based on assumptions with regard to their culture, class, gender, etc. this in turn leads to assumptions on how they may react in a situation, dress, use products, appreciate aesthetics and so on.
White in many cultures symbolizes, purity, elegance and peace. Brides often where white wedding gowns. In some cultures however white represents, death, mourning or bad luck and white is traditionally worn at funerals. In Australia and China, to turn a light switch it is flipped down. In the USA it is flipped up.
Stereotyping brings advantages and disadvantages for designers and users.
Advantages:
Allows you to form assumptions and associations about a group of people.
Judgements and decisions can be made quickly.
Possibly predict the behaviour or possible use of a product or system.
The user needs and behaviour can be identified and thus usability considerations are met.
Disadvantages:
Assumptions and associations of a particular stereotype may not fit all people of that population.
Judgements and decisions could be incorrect.
Not all people who ‘look alike act/think alike’ therefore behaviour or the way a product was intended to be used may be wrong.
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