Design & EvaluationChapter 3

Rebecca W. Boren, Ph.D.Arizona State University

IEE 437/547September 13, 2010

The goals of enhancing performance, satisfaction, and safety are attained by several methods including Conducting basic and applied research to

broaden our understanding Applying human factors principles, methods,

and data to the design of new products or systems.

What is Human Factors Design?

The Design of

New products or systems

The Design of Modifications for existing products or

systems

Stay fresh packaging for food,

RFID

The Design of

Ergonomically sound environments

The Design of

Safety-related activities

Beware of ergonomic claims

All claim to be modern andErgonomic.

The Design of Training programs

& support material

Driving simulator

Driving safely asYou get older.

How?

You will learn the tools of human factors design in later chapters of the textbook.

First, you must determine the users’ needs.

What is the First Law of Human Factors Design?

What is the First Law of Human Factors Design?

“Know The User”for

The User is Not You.

Methods to determine needs Describe the population of users

Observation Interviews Questionnaires Task analysis & flowcharts Describe environmental conditions Identify user preferences Analyze data collected

Many products and systems are still designed and manufactured without adequate consideration of human factors.

Many products and systems are still designed and manufactured without adequate consideration of human factors.

What is the problem?

As products become more technologically sophisticated they frequently become more difficult to use.

Product may be completed and then given to a human factors specialist to evaluate.

Problems with that?

Human factors design can save companies time and money. To get the full benefit, human factors methods must be applied early in the design process.

The best way to demonstrate the value of human factors to management is to do a cost/benefits analysis.

HF analysis is an extra cost. Must be justified.

What are the costs?

What are the costs?

Wages to human factors specialist Materials used in questionnaires, computers,

recording equipment. Lost productivity for workers during study These are only examples.

What are the benefits?

Benefits need to be quantifiable. Some examples: 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,

What are the benefits?

Some more examples: Decreased training time, Decreased user turnover. Increased employee satisfaction (lower turnover) Decreases in sick leave Decrease in number of accidents or acute injuries Decrease in number of chronic injuries (e.g.

cumulative trauma disorders) Reduction in medical and rehabilitation expenses Reduction in number of citations, fines, or lawsuits

Even small cost savings per task can add up in the course of a year. Example:

Development of software used by 240,000 employees.

Human Factors design cost was $6,800 Time-on-task monetary savings $6,800,000 for

first year alone.

Must adequately determine user needs. General approaches

Early focus on the user and tasks Empirical measurement using questionnaires,

usability studies, and usage studies focusing on quantitative performance data.

Iterative design using prototypes Participatory design (where users are directly

involved as part of the design team)

Human factors in the product design lifecycle

Front-end analysis Iterative design and testing System production Implementation & evaluation System operation & maintenance System disposal

What is the most effective way to involve human factors in product design?

What is the most effective way to involve human factors in product design?

All through the design process

Who might be included in a team? Example: personnel from marketing Who else?

What is user-centered design? ‘Honor the user’ or ‘Know the user’ Find a system design that supports the

user’s needs rather than making a system to which users must adapt.

Must adequately determine user needs.

Front-end Analysis. Before the design solutions are generated, be able to answer the following questions Who are the users? (also people who maintain,

monitor, repair and dispose of the system) What are the major functions to be performed by

the system? What tasks must be performed? What are the environmental conditions under

which the system will be used? What are the user’s preferences or requirements

for the product?Example of laptop computer.

User Analysis

Create a complete description of the population of users (gender, age, educational level, physical size, any disabilities, familiarity with the type of product, and task-relevant skills)

Personas: a hypothetical person that represent key characteristics of the user population. (Personas exist to define the goals that the system must support and describe the capabilities and limits of users in concrete terms)

Remember: “The user is not you.”

Task analysis

Specifies the jobs, duties, task and actions that a person will be doing. Detailed and specific.

Tasks can be physical or cognitive

How can we perform a task analysis?

How to perform a task analysis Description of tasks

Hierarchical relationships Information flow Task sequence Location and environmental conditions

Collect task data Observation Think-aloud verbal protocol Interviews Surveys and Questionnaires

Continued …

Analyze task data Identify user preferences and requirements

Related to marketing Users don’t always prefer what is best for

them.

User Needs

Evaluation

Design

Refine

Design is an Iterative Process

Evaluation of design

Mock-up

or prototype

Prototyping

Mock-ups are crude approximations Prototypes have more of the look and feel

and may have some functionality Paper prototypes of software systems are

screen designs sketched on paper.

Evaluation of design

Mock-up or prototype Use data compendium or standards Heuristic evaluation by an expert Usability testing

Resources for Design Work

Data Compendiums Human Factors Design Standards (military

standards, ANSI/HFES-100 VDT) Requirements and recommendations.

Human Factors Principles & Guidelines (presented in the textbook after chapter 3)

Heuristic design evaluation

Refers to a systematic evaluation of the product design to judge compliance with human factors guidelines or heuristics.

Usually performed by usability experts and does not include end-users.

Usability testing

Needed if the system involves controls and displays with which the user must interact

Usability is primarily the degree to which the system is easy to use or “user friendly.”

Who or what is being tested?

Usability testing

Example of testing an infant car seat.

Usability testing measures

Learnability (how easy the system is to learn)

Usability testing measures

Learnability Efficiency (high level of productivity

is possible)

Usability testing measures

Learnability Efficiency Memorability (casual user can return

to the system after some period of not having used it, and without have to relearn the system)

Usability testing measures

Learnability Efficiency Memorability Errors (few errors, easy recovery

from errors, no catastrophic errors occur)

Usability testing measures

Learnability Efficiency Memorability Errors Satisfaction (users like the system)

Usability testing measures

How many subjects are enough for usability testing?

Usability testing measures

How many subjects are enough for usability testing?

Ans: 4 to 5

Questions?