An Introduction to Human Factors
Engineering Summary
1. INTRODUCTION TO HUMAN FACTORS
1.1 WHAT IS THE FIELD OF HUMAN FACTORS?
The goal of human factors may be defined as making the human interaction with systems one that
enhances performance and increases safety, health, usability and user satisfaction.
Human factors involves the study of factors and development of tools that facilitate the
achievement of these goals. We will see how the goals of productivity and error reduction are
translated into the concept of usability, which is often applied to the design of computer systems. In
achieving these goals, one should realize that there are often tradeoffs between them (for example
enhanced productivity vs. compromised safety).
The human factor cycle depicts the human operator (brain
and body) and the system with which he or she is
interacting. Point A identifies a cycle when human factors
solutions are sought because a problem has been observed
in the human-system interaction. Point B shows the five
different approaches directed toward implementing a
solution after the problem is identified:
1. Equipment design changes the nature of the
physical equipment with which humans work.
2. Task design focuses more on changing what
operators do than on changing the devices they use.
3. Environmental design implements changes in the
physical environment where the task is carried out.
4. Training focuses on better preparing the actor for the task at hand.
5. Selection is a technique that optimizes performance by selecting the most suitable and
skilled operator for the job.
1.1.1 The Scope of Human Factors
The ultimate goal of the study of human factors is toward system design, accounting for those
factors, psychological and physical, that are properties of the human component. Human factors
places great emphasis on developing usable design principles. All in all, the scope of human factors
can be broadly specified as any interaction between human actors and their sensory components
(such as perception, motor control, cognition and vision) and systems in a contextual environment.
1.1.2 The Study of Human Factors as a Science
Characteristics of human factors as a science relate to the search for generalization and prediction.
In the problem diagnosis phase (Point A in the figure) investigators wish to generalize across classes
of problems that may have common elements. Furthermore, it is also important to be able to predict
that solutions designed to create good human factors will actually succeed when put into practice. A
critical element to achieving effective generalization and prediction is the nature of the observation
or study of the human operator.
, 2. DESIGN AND EVALUATION METHODS
The goal of a human factors specialist is to make systems successful by enhancing performance,
satisfaction, and safety. In addition to conducting basic and applied research to broaden our
understanding, this is done primarily by applying human factors principles, methods, and data to the
design of new products or systems.
2.1 OVERVIEW OF DESIGN AND EVALUATION
Many, if not most, products and systems are still designed and manufactured without adequate
consideration of human factors. Designers tend to focus primarily on the technology and its features
without fully considering the use of the product from the human point of view. Poor design is
common, and as our products become more technologically sophisticated, they frequently become
more difficult to use. To maximize the benefits achieved by applying human factors methods, the
activities must be introduced early in the system design cycle. The best way to demonstrate the
value of human factors to management is to perform a cost/benefit analysis.
2.1.1 Cost/Benefit Analysis of Human Factors Contributions
In a cost/benefit analysis, one calculates the expected costs of the human factors effort and
estimates the potential benefits in monetary terms. Estimating the costs for a human factors effort is
relatively easy because the designer tends to be familiar with the costs for personnel and materials.
Estimating the benefits tends to be more difficult and must be based on assumptions. Nine benefits
that might be applicable and that can be estimated quantitatively are: increased sales, decreased
cost of providing training, decreased customer support costs, decreased development costs,
decreased maintenance costs, increased user productivity, decreased user errors, improved quality
of service, decreased training time and decreased user turnover. Other quantifiable benefits are
health or safety related such as increased employee satisfaction or decreases in sick leave.
2.1.2 Human Factors in the Product Design Lifecycle
One major goal in human factors is to support the design of products in a cost-effective and timely
fashion, such that the products support, extend, and transform user work. As noted earlier, in order
to maximally benefit the final product, human factors must be involved as early as possible in the
product (or system) design. Six major stages of human factors in the product life cycle include: (1)
front-end analysis, (2) iterative design and test, (3) system production, (4) implementation and
evaluation, (5) system operation and maintenance and (6) system disposal.
2.1.3 User-Centered Design
User-centered design centers the design process around the user and not the technology. This is
done by adequately determining user needs and involving users at all stages of the design process.
2.2 FRONT-END ANALYSIS
The purpose of a front-end analysis is to understand the users, their needs, and the demands of the
work situation. In general, the designer should be able to answer the following questions before
design solutions are generated in the design stage:
1. Who are the product/system users?
2. What are the major functions to be performed by the system, whether by person or
machine? What tasks must be performed?
3. What are the environmental conditions under which the system/product will be used?
4. What are the user’s preferences or requirements for the product?
,2.2.1 User Analysis
Before any other analysis is conducted, potential system users are identified and characterized for
each stage of the system lifecycle. The most important user population are those people who will be
regular users or ‘operators’ of the product or system. Characteristics such as age, gender, reading
ability, physical abilities and task-relevant abilities should be included in a complete description of
the potential user population. One way to describe the user characteristics is through the concept of
personas. A persona is a hypothetical person developed through interviews and observations of real
people in the user population.
2.2.2 Environment Analysis
In most cases, the user characteristics must be considered in a particular environment. Activities or
basic tasks that are identified in the task analysis should be described with respect to the specific
environment in which the activities are performed.
2.2.3 Function and Task Analysis
During the function analysis, the human factors specialist performs an analysis of the basic functions
performed by the system listing the general categories of functions served by the system. Functions
represent general transformations of information and system states that help people achieve their
goals but do not specify particular tasks. Task analysis is one of the most important tools for
understanding the user and can vary substantially in its level of detail. Depending on the nature and
complexity of the system being designed, the human factors specialist might need to perform an
activity analysis specifying the jobs, duties, tasks and actions a person will be taking. Goals, functions
and tasks are often confused, but they are not the same. A goal is an end condition or reason for
performing the tasks. Functions represent the general transformations needed to achieve the goal,
and tasks represent the specific activities of the person needed to carry out a function.
2.2.4 How to Perform a Task Analysis
Most generally, a task analysis is a way of systematically describing human interaction with a system
to understand how to match the demands of the system to human capabilities. The following steps
describe the basic elements of a task analysis:
Define the analysis purpose and identify the type of data required
Collect task data
Summarize task data
Analyze task data
2.2.4.1 Define Purpose and Required Data
Because a task analysis can be quite time consuming, it is critical to focus the analysis on the end-use
of the data. Both the purpose and the type of the task (physical or cognitive) will influence the
information gathered. Tasks can be described by several types of information:
Hierarchical relationships – describe how tasks are composed of subtasks and how groups of
tasks combine into functions
Information flow – describes the communication between people and the roles that people
and automated systems play in the system
Task sequence – describes the order of tasks and the relationship between tasks over time
Location and environmental conditions – describe the physical world in which tasks occur
Moreover, and most importantly, a task analysis should record instances where the current system
makes it difficult for users to achieve their objectives. Such data can identify opportunities for
redesigning and improving the system.
, 2.2.4.2 Collect Task Data
A task analysis is conducted by interacting extensively with multiple users. The particular data
collection approach depends on the information required for the analysis. Ideally, human factors
specialists observe and question users as they perform tasks. Approaches include:
Observation. Observe users using existing versions of the product or system. Observations
can often be much more valuable than interviews or focus groups because what people
think and say does not always match what they do.
Think-Aloud Verbal Protocol. Have users think out loud as they perform various tasks. This
yields insight into underlying goals, strategies, decisions, and other cognitive components.
Task Performance with Questioning. Ask users to perform the tasks while answering
questions.
o Advantage: may cue users to verbalize their underlying goals or strategies more.
o Disadvantage: can be disruptive.
Unstructured and Structured Interviews. Ask users during interviews to describe the general
activities they perform with respect to the system. Unstructured: no particular method for
structuring the conversation, usually with open questions. Structured: interview process
more pre-defined and efficient, usually with more closed questions. Focus groups are
another interview approach and use a group of people with a facilitator to accommodate for
a discussion rather than a conversation.
Surveys and Questionnaires.
Limitations. The analysis should focus on the basic user goals and needs, and not exactly on how
they are carried out using the existing products. It is critical to analyze the task data to identify new
design concepts that help people achieve their goals rather than to design to fit the current tasks.
2.2.4.3 Summarize Task Data
Once task-related information has been gathered, it must be documented and organized in some
form. Often, several forms are commonly used in conjunction with one another: (1) lists, outlines,
and matrices; (2) hierarchies and networks; and (3) flow charts, timelines and maps.
Lists, Outlines and Matrices. Task analysis usually starts with a set of lists and then breaks
the tasks down further into subtasks developing tables or matrices specifying related
information for each task or subtask.
Hierarchies. The disadvantage of using outlines or tables is that tasks tend to have complex
hierarchical organizations, and this is easiest to represent and analyze if the data is
graphically depicted in a hierarchical chart that organizes tasks as sets of actions used to
accomplish higher level goals.
Flowcharts, Timelines, and Maps. Flowcharts capture the chronological sequence of subtasks
as they are normally performed and depict the decision points for taking alternate
pathways.
All of these methods have advantages and disadvantages, and choosing the most appropriate
method depends on the type of activity being analyzed. If the tasks are basically linear and usually
done in a particular order, it is appropriate to use an outline or flow chart. If there are more
cognitive elements and many conditions for choosing among actions, hierarchical formats are more
appropriate. Important in developing efficient interfaces, designers must consider the hierarchical
structure and the linear sequence of tasks.
2.2.4.4 Analyze Task Data
The analysis of these data can include intuitive inspection, such as examining a flowchart diagram to
identify redundant tasks. Frequently, simply inspecting graphics or summary tables, however, cannot
