Usability and Task Analysis

Overview and Terminology

• Motivation and History - Roots in Human Factors and Ergonomics
• Recent Focus on Usability (including of Web)
• Accessibility and Accessible Design
• Universal Design
• Relation to medical device regulation: focus on safe use.

Systems Analysis

• Overall System
• Interface Analysis - Information and Power Transfer
• Human Performance Considerations

Universal Design (Universal Accessibility/Usability)

• Principles and Guidelines
• Performance Measures Related to Universal Usability
• Accessible/Universal Design Performance Measure for Products

Considerations in Usability and Task Analysis

• Approaches
• Features of a Usability Lab
• Mobile Usability Lab

Terminology and Concepts

Human Factors and Ergonomics

Human factors focuses on designing system interfaces to optimize the user’s ability to accomplish tasks successfully and error-free within a reasonable time period. It is an applied science with roots in understanding how people use tools, with the dual mission of enhancing performance while also minimizing the risk of human error, injury or frustration.

Ergonomics is often used interchangeably with human factors, and indeed the key professional society for the field is the Human Factors and Ergonomics Society (HFES) Ergonomics has historical roots that are closer to biomechanics and injury analysis, while the roots of human factors are more in psychophysical task analysis. This is reflected academically, as most strong ergonomics programs have their roots in engineering departments and occupational health, while most strong human factors have their roots in psychology departments or industrial engineering departments that have a history of tight ties to the military or space industries.

Usability

Usability, or the ability to use, refers to the extent to which a product can be used by specified users to achieve specified goals in an effective and efficient manner, to the satisfaction of these users. In recent years this term has taken on great significance within industry, and terms such as usability engineering and user-centered design are now in common use. Many companies designing consumer products now have in-house usability labs. Practical components of a user-oriented design include:

• ease of learning,
• high speed of user task performance,
• low user error rate,
• subjective user satisfaction, and
• user retention over time.

In recent years there has been increasing use of computers within society, including the clinical environment. Much of the target of usability activity relates to human-computer interaction (HCI) and interface design, with a focus on optimizing human performance and ease of use.

In some fields, such as in medical devices where there can be serious consequences of , there is also a strategic focus on use errors.

Accessibility and Accessible Design

Accessibility, or ability to access, has been defined multiple ways. One type of definition has its roots in human rights, and views accessibility as the ability to access the benefit or functionality of a given product, service or environment. This type of definition has its roots in human rights, and is the foundation for the many legal mandates for accessibility. It is also defined sometimes as effective use of a product by all people, including persons with disabilities. Such a definition focuses on the use of an interface, rather than the benefit. We will talk more about the concept of access, and its implications, in the next module.

Accessible design targets removing barriers that prevent the person from participating in the use of a product, i.e. extending a design to maximize the number of potential customers who can readily use the device or service. In some cases there are legal mandates that specify what constitutes an accessible design.

While there is often synergy with usability (e.g., ease of use is desirable) and accessibility is sometimes considered a category of usability, at times making an interface more fully accessible may lower the degree of usability for some. This was spelled out in a recent book chapter by this author, parts of which you will be reading in the next module. For instance, an interface may appear more complex when multimodal options are added that make it accessible to more people. Multimodality refers to support for transformations to alternative sensory interface modes for a channel (e.g., between text and speech), such that more than one modality is available. There are two basic strategies for enhancing access: "direct access" (direct adaptations to product designs that significantly include their accessibility) and "assistive access" (product interface(s) that enable(s) an add-on assistive technology to provide the user with access). Legislation such as Section 508 of the Rehab Act, which we will be discussing further in the next module, allows either strategy.

Universal Design

Universal Design is the design of products and environments to be effectively and efficiently usable by people with a wide range of abilities, to the greatest extend possible, without the need for adaptation or specialized design. Seven principles, based on a consensus process organized starting in the 1990s that was coordinated by the Center for Universal Design at North Carolina State University, follow:

1. Equitable Use
2. Flexibility in Use
3. Simple and Intuitive Use
4. Perceptible Information
5. Tolerance for Error
6. Low Physical Effort
7. Size and Space for Approach and Use

It clearly relates to usability and accessibility, and can be viewed as maximizing the "direct access" approach to achieving accessibility. The concept of universal usability, i.e. usable by all, fits well with the concept of universal design. Indeed, the Universal Design Performance Measures for products can be viewed as a tool for assessing universal usability.

Other concepts that are similar in concept, especially in Europe and Japan, are Transgenerational Design, Inclusive Design and Design-for-All.

Universal Access and Universal Usability

Universal Access is simply access by all to the full benefits of an entity (product, service, or environment). Universal usability simply means that everyone can fully use an entity (product, service, or environment). Both are, of course, difficult to fully achieve.

While the terms usability, accessibility and universal design all involve levels of degree, in the limit they tend to converge. In my opinion the most general term is Universal Access in that it includes the barriers of distance and time as well as a universally designed and usable interface.

"Systems" Perspective of Human Factors and Usability Analysis

For human factors/ergonomic/usability analysis, it is useful to consider the "system" to involve one or more individual users plus the technology that they are using to perform tasks of interest. The human-technology "interface" thus becomes a connection between subsystems. The modes of transfer between subsystems may include two types:

• undirectional information transfer, normally with a sensory channel (auditory, visual, tactile) receiving information from a motor channel of another person (speech, eye-head-hand-torso postural orientation, hand manipulation) or from the environment.
• bidirectional power transfer, normally through physical contact, where there is instantaneous 2-way force-velocity transmission (e.g., see discussion of Extended Physiological Proprioception)

This is an "interface port" conceptual framework. There are many other "systems" concepts that can be of value for usability analysis. For instance, there are "human operator" models for goal-directed pursuit tracking tasks that represent the human response to a stimulus as a time lag plus low-pass filter. This is simplistic but can be useful for analysis or design within a controlled environment such as a cockpit. There is also the HAAT conceptual model that considers performance of the human and assistive technology as a system. While a simplification, for a reasonably well-defined type of activity, performance of the combined intrinsic and extrinsic enables can be a useful tool for analysis.

Considerations in Usability and Task Analysis

A number of usability methods have been described in the literature, such as cognitive walkthrough (where evaluations/users systematically document and talk through the goals and steps involved in using the interface), and heuristic evaluation (where usability specialists determine whether each element of a user interface follows established usability principles). An example of rules of thumb for heuristic evaluation of user interfaces comes from Jacob Neison, considered one of the pioneers in the area:

• Visibility of system status.
• Match between system and the real world.
• User control and freedom.
• Consistency and standards.
• Error prevention.
• Recognition rather than recall.
• Flexibility and efficiency of use.
• Aesthetic and minimalist design.
• Help users recognize, diagnose, and recover from errors.
• Help and documentation.

The above is quite general. There are also approaches for specific areas, such as web- and computer-based design. An example is the document from the usability.gov site.

Here we are especially interested in usability/ergonomic analysis that targets activities/tasks using devices where the performance goals are clearly identifiable. Often such activities can be broken into a sequence of subtasks (e.g., stages related to positioning, mobility, reaching, manipulation, and communication). Each of these can be broken down further, and there are many such classification schemes. For instance, the RERC-AMI is working on such schemes, and some of these may be presented in class.

Of note is that generally-speaking, observations of performance are not sufficient for task analysis, except for very simple tasks. Sensors and observers simply cannot get into the mind of the user. Normally the usability engineer must also employ methods that extract information from the subject/client, for instance related to their understanding of a product, the choices they made to perform a task, their opinions of a product, and perhaps their suggestions for improvement. Often this takes the form of both a structured questionnaire or interview, and an open-ended stage. Normally such information collection immediately follows performance of the activity. The MU-Lab is an example of such an instrument.

Safe Use and Access of Medical Devices and the FDA

Another perspective comes from the FDA and it's Center for Devices and Radiological Health, which has the responsibility for regulating medical devices (including "durable medical equipment" such as wheelchairs). Considering that the eighth leading cause of death in the U.S. is said to be medical error, and that many homecare/rehabilitation technologies have migrated into the home (often used by persons with functional limitations), the FDA has developed a clear interest in encouraging human factors in medical product design. The FDA's Human Factors Program has produced documents and supported standards activities that provide a different type of "systems" perspective, targeted to help companies minimize user risks and provide error tolerance, including:

• Do it by Design: An Introduction to Human Factors in Medical Devices (by FDA's D. Sawyer, 1996)
• Medical Device Use-Safety: Incorporating Human Factors
  Engineering into Risk Management (by FDA's R. Kaye and J. Crowley, 2000)
• AAMI / ANSI HE74-2001 Standard: Human Factors Design Process for Medical Devices

Other important terms, especially for medical products, include reliability, safety and efficacy. Practitioners in particular have little patience for new products that are not immediately reliable.