Copyright 2000 by Dr. Craig M. Harvey, Wright State University Dr. Craig Harvey 1 User Centered...

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Copyright 2000 by Dr. Craig M. Harvey, Wright State University

Dr. Craig Harvey

User Centered Design

HUMAN FACTORS

ERGONOMICS

HUMAN ENGINEERING

ENGINEERING

PSYCHOLOGY

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Dr. Craig Harvey

Human-Machine Model

PROCESSING

SENSORY

EFFECTORS CONTROL

DISPLAY

ENVIRONMENT

WORK ORGANIZATION

WORKSPACE

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Human Component Effectors Senses Supportive Processes

Machine Component Controlled Process Displays Controls

Environment Workspace Physical Environment Work Organization

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What is Good Design?

Subsidiary questions: What are interactive systems? Why do we design them? How do we know if we’ve succeeded? What happens if we fail? How do we maintain a track record of success in design? How can we also retain our creativity?

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Dr. Craig Harvey

Subsidiary Questions

What are interactive systems? The user interface Technocentric versus anthropocentric approaches

Why do we design them? To resolve a situation of concern

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Success?

How do we know if we’ve succeeded? By testing whether the situation is resolved

But we can’t do this during design By measuring or predicting usability

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The Need for Usability Analysis

The need arises when we’re faced with the following kinds of questions during design:

Will the operator be able to handle emergency telephone calls faster than before?

Have we simplified the design of this ticket machine to a point where people will use it successfully on their first attempt?

Is the small size of this screen target

going to result in a significant number of

errors in selecting it? If the user invokes this command by mistake,

will he or she find the escape route?

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Dr. Craig Harvey

The Need for Usability Analysis

Will the word-processor user remember that there are three different ways of changing the properties of a formatting style?

Is it so difficult to change the layouts of menus that hardly any users will bother?

Once the system is set up to support work-groups of a particular size and structure, how much effort is involved in changing the system to support changes in the group?

How many of the people who try the system

will actually continue to use it?

To answer these questions, we analyze the

design in terms of its usability.

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Dr. Craig Harvey

Usability Factors

The speed of performance of the activity, which affects how many people are needed to perform it

The incidence of errors while performing the activity

The user’s ability to recovery from errors that occur

The magnitude of the user’s task in learning to use the system

The user’s retention of learned skills

The user’s ability to customize the system to suit their way of working or the situation of use

The ease with which people can reorganize

activities supported by the system— their own

activities and other people’s

Users’ satisfaction with the system.

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Dr. Craig Harvey

What happens if we fail?

Examples of failure:

• London Ambulance Service, 1992

• USS Vincennes’ Aegis weapons system

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Breakout #1

Divide into your groups

Do the following: Watch the demonstration video. List all the usability issues you can identify in the use of this product.

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Dr. Craig Harvey

Fundamentals of Interactive System Design

Identifying the human activity that the proposed interactive system will support

Identifying the people, or users, who will perform the activity

Setting the levels of support that the system will provide, otherwise known as the system’s usability

Selecting the basic form of solution to the design problem.

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Product Development Phases

Definition of Need

Detail Design &Development

Conceptual Design

PreliminaryDesign

?

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Dr. Craig Harvey

Usability touches each phase of Product Development

Usability

Definition of Need

Detail Design &Development

Conceptual Design

PreliminaryDesign

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Using Human FactorsTools & Techniques

Prototyping

Guidelines

Video Analysis

Empirical Analysis

Focus Groups

“ Information is the

”

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Two Ways of Assessing Usability

Analytically - by simulating how the user’s activity will be performed

Empirically - by building and testing a prototype

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Analytical Methods Advantages

Analytical methods have advantages: We can test designs that we can’t build

We can save time by not building a prototype

We don’t need to plan and conduct an experiment

In other words, they can be used more quickly, earlier in the design

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Empirical Methods Advantages

Empirical methods have advantages: We receive more precise information about how a user will interact

with the product

We can see major flaws easier and therefore reducing modifications to the product once it is fielded

In other words, it will provide richer information; however, there is are also increased costs associated with the experimentation

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Two Type of Information

Qualitative

Quantitative

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Definition of the Need

Interviews

Conceptual PreliminaryDesign

DetailedDesign

Tools & Techniques

Qualitative

Quantitative

Function Allocation

Questionnaires

Focus GroupsPrototypes

Anthropometrics

Heuristics

Cognitive Walkthrough

Task Analysis

Guidelines

|Q.F.D.

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Dr. Craig Harvey

Interviews

Purpose: Useful for reaching target populations and gathering rich information

Types: structured, unstructured

Making sure the following are covered: The interview’s purpose, explained at the outset. Enumerating activities by asking a general

question, e.g., “What are your tasks?” and following this up with more specific questions.

Work methods: finding out how tasks are performed.

Performance issues. These provide a measure

of the “usability” of the current support system

and the need for improvement.

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Questionnaires

Purpose: Useful for reaching large populations and thus gathering large amounts of data

Issues to consider in design: The need to make things easy for the subject. The need for unambiguous questions. The need to gather precise data. The need to support the intended analysis.

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Dr. Craig Harvey

Focus Groups

Purpose: Useful for reaching target groups of users to get consensus information on product information

Method:Facilitated workshops of groups of 5-10 people - current or likely users

Type of Information:subjective (tasks, requirements, product ideas, etc.)

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Function Allocation

Purpose: To determine the allocation of all functions to either humans or machines.

• Human and machines have different capabilities (strengths and limitations). e.g.,

Human Machine complex pattern recognition (e.g.,

aerial photography) sensing outside range of

human sensitivities unexpected events predefined infrequent events adapting to decisions to situational

requirements (e.g., emergencies)

rapid and consistent responses to a given input

concentrate on important activities in overload conditions

perform several activities simultaneously

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Function Allocation Strategy

Mandatory - system requirements, safety, legal or labor constraints, etc.

Balance of value - assignment based on relative performance

Utilitarian - human is available and is capable

Cost-based - relative cost of performance

Affective and cognitive support – meaningful work and maintaining adequate knowledge of the system

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Dr. Craig Harvey

Guidelines

Purpose: Guidelines provide us with advice on the solution of design problems.

They suggest possible solution strategies. Each guideline has a context or domain within which it applies. Guidelines act as heuristics, drawing on assumptions derived from

past experience. In many cases, the experience we draw on includes empirical

research.

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Roles of Guidelines

Raising awareness of concepts

Assisting in design choices

Offering strategies for solving design problems

Supporting evaluation

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Limitations of GuidelinesProblems in selecting guidelines: the tendency to apply the first guideline that seems relevant

Problems in applying guidelines, e.g., from Tullis (1988): Example: Reduce search times by minimizing the number of groups of items while designing each group to subtend a visual angle as close as possible to 5 degrees Does this apply to our problem? Will it have the desired effect? Will the resulting design really be more

usable?

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Contexts of Guideline Use

Check the guideline against the problem statement: Is the guideline appropriate to the activity that the design is to

support? Is it applicable to the type of user who will perform the activity? Does it address the particular levels of support or usability factors

that determine the success of the design? Is it appropriate to the form of solution chosen?

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Guideline Categories

Five contexts that cover the spectrum of guideline use: General principles that apply to any user interface Guidelines that apply to forms of solution for interactive display

layouts, including those that use color Guidelines for use with specific interaction styles Sets of guidelines offered in style guides associated with proprietary

systems and standards Guidelines for the design of individual user interface components

supporting particular user tasks.

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Two universal principles: Design with a view to supporting the user’s task or process. Know the user (Hansen, 1971 in Newman and Lamming,1995).

Suggested general principles:Shneiderman (1992) Nielsen and Molich (1989)Strive for consistency. Be consistent.

Enable frequent users to use Provide short cuts.

shortcuts.

Offer informative feedback. Provide feedback.

Design dialogues to yield closure. Good error messages.

Offer simple error handling. Provide clearly marked exits.

Permit easy reversal of actions. Support internal locus of control.

Reduce short-term memory load. Minimize user memory load.

Simple and natural dialogue.

Speak the user’s language.

Prevent errors.

General Design Principles

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Examples of Guidelines

Make all facets of design consistent with user expectations considering both the user’s prior experience and well established conventions, such as symbologyDesign workstations, controls, and displays around the basic capabilities of users regarding such characteristics as strength, dexterity, memory, reach, visual acuity, and hearingBe sure that auditory signals are well within users’ threshold values for amplitude and frequency considering the effects of ambient noiseBe sure the brightness of visual signals must be sufficient to be perceived by users working under various conditions of ambient illumination and that the brightness and contrast are adequate to optimize legibilityBe careful that labels and displayed information

are easy to read from the typical viewing angles and distances. Symbol size, contrast, color, and display depth must be considered.

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Examples of Guidelines

GOGOPush the

Button

downOne Way

Ensure abbreviations, symbols, text, and acronyms placed on, or displayed by, the device are also used in the instructional manual

Design control knobs and switches to correspond with both general conventions and any that are unique to the user population

Arrange and design knobs, switches, and data-entry key in a way that reduces the likelihood of accidental activation

Use color and shape coding to facilitate the rapid identification and discrimination of controls and displays. Color and codes should correspond to universal industry convention.

Space keys, valves, and control knobs sufficiently apart for easy manipulation. This will also reduce likelihood of accidental

activation.

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Anthropometrics

Purpose: The workplace should be suited to the human operator.

Method: There is enormous variation between individuals. The most important differences in size are due to sex, age, and race.

Type of Information: 5th, 50th, & 95th percentile measurements of body, strength, and joint rotations.

Source of Information: Anthropometric data tables.

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Performance Task Analysis

Time

Errors

Quality

Quantity

Workload, etc.

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Methods of Performance Analysis

Three widely-used methods: GOMS analysis methods, including keystroke-level analysis

Heuristic evaluation: introducing walkthrough and performance analyses as needed

Cognitive walkthrough, in which performance analysis is folded into the sequence analysis

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Two Stages of Analysis

We are making predictions about how a human activity, performed as a sequence of steps, will be supported.

So:1. We must establish the sequence of steps

2. We must analyze the performance of each step

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GOMS Analysis

Analysis in terms of four components of the activity: Goals that users are trying to achieve

Operators, i.e., basic actions that users perform

Methods employed by users to attain goals, made up of sequences of operators

Selection rules for choosing between methods

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Dr. Craig Harvey

Heuristic Evaluation

Can be applied to problems where GOMS and Cognitive Walkthrough are unsuitable, i.e.: (a) method of operation is not fully predictable, and (b) user is not a complete novice

The Heuristic Evaluation method: employ a team of evaluators to identify problems in the

design provide a list of heuristics (general guidelines) to guide

their evaluation, e.g.: Simple and natural dialogue Provide clearly

marked exits Speak the user’s language Provide short cuts Minimize user memory load Good error

messages Be consistent Prevent errors Provide feedback

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Dr. Craig Harvey

Advantages of Heuristic Evaluation

Low cost

Intuitive to perform

Requires little training

No advance planning required

Can be used early in the design process

Provides high-level evaluation, but inherently less repeatable than other analysis methods

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Alternate Set of Heuristics

Learning: Help and Documentation:

design for use without documentation provide easy-to-use task-oriented documentation

Adopt the User’s Viewpoint: speak the user’s language (avoid jargon) make use of existing knowledge

Simple and Natural Dialogue: avoid extraneous information, steps, actions information should be in a logical, natural

order Design for Advancement:

provide shortcuts (quick keys, customization)

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Adapting to the User: Provide Maps and a Trail:

give the user a way to preview where to go and what will happen give the user a way to review and return to previous contexts

Show the User What is (Not) Possible: provide affordances to indicate what can be done

Intuitive Mappings: design good response compatibility between controls and actions

Minimize Memory Load: remove the need to remember across dialogues provide multiple views for easy comparisons

Consistency in the System and to Standards: make sure the same term / action has one

meaning when there is no better way, conform to a

standard

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Feedback and Errors: Feedback:

provide timely feedback about all processes and system status

Prevent Errors: make it difficult to make errors

Error Messages: diagnose the problem and suggest a solution

Clearly Marked Exits and Error Recovery: make sure the user can get out of an

undesirable state easily design assuming that people will make

errors and need to recover previous states

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Find evaluators: independent usability AND application experts.

Apply heuristics: apply each heuristic to many parts of the system. apply heuristics while completing benchmark tasks.

Enter violations into a database or form: evaluator records problems or observer takes notes on evaluator.

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Number Problem ID

Task What task (ID) were you working on?

Problem Describe the problem. Use the first line as a summary.

Heuristic What heuristic(s) (ID) were violated?

Severity Rate the problem severity.0=none 1=cosmetic 2=minor 3=major 4=catastrophic

Generality Rate how widespread is the problem:1=single-case 2=several-places 3=widespread

Solution Suggest solution(s), noting tradeoffs.

Evaluator Add an evaluator ID if needed.

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Breakout #2

Divide into your groups

Using the provided devices: PART 1: perform a heuristic evaluation using the calculator to

perform the following math function to solve for y. y = (3)2 * (40)-6 + 1000 – 7*100 + (-100)

PART 2: perform a GOMS analysis of the setting the time on your watch to central time.

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Cognitive Walkthrough Analysis

Purpose: A method for analyzing walk-up-and-use interfaces for ease of learning by first-time users.

Based on a model of exploratory learning : The user starts with a rough plan of what he or she wants to achieve—a

task to be performed;

The user explores the system, via the user interface, looking for actions that might be contribute to performing the task;

The user selects the action whose description or appearance most closely matches what they are trying to do;

The user then interprets the system’s response and assesses whether progress has been made towards completing the task.

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Determining the Sequence

Earlier, we discussed two methods of analysis: Analytically - by analyzing the options available to the user at each

step—a form of Walkthrough Empirically - by studying how the user performs the activity, and

choosing a representative (‘benchmark’) sequence.

Walkthroughs play a double role: in determining the sequence analytically in performing step-by-step analysis of performance

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Steps in Conducting aCognitive Walkthrough

Identify what the user is trying to do, and then ask the following questions repeatedly:Q1: Will the correct action be made sufficiently evident to the user?

Q2: Will the user connect the correct action’s description with what they are trying to do?

Q3: Will the user interpret the system’s response to the chosen action correctly, i.e., will they know if they have made a right or wrong choice?

The result is to expose design flaws that may interfere with exploratory learning.

The method is best applied by small teams walking through the design together.

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Observation

Field study versus laboratory study

Video recording

Concurrent verbal protocols

Passive observation

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Prototypes

Purpose (Newman and Lamming, 1995) : – design and implement a complete user interface, so that

the system can be tested on externally valid tasks– to do this under tight time constraints, by making use of

appropriate prototyping tools.

Type of Information: – discovering problems in the design

that were not apparent on paper.

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Prototype Stages1. Identifying key properties. We focus on properties identified in the problem

statement or in early requirements documents.

2. Developing the prototype. All we need is a prototype thata) has the functions to support the tasks of interestb) has the performance to allow a realistic test andc) has enough robustness to survive each test without serious failure.

3. Experimental design. We need a small number of users, to whom we set a suitable range of benchmark tasks, chosen to exercise the prototype’s functionality as fully as possible.

4. Collecting data. Direct observation and recording of video and concurrent protocols are especially effective.

5. Data analysis. The good and bad features of the design will probably be obvious right away; we may also take simple performance measurements.

6. Drawing conclusions. The primary outcome of informal testing is a list of design changes.

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Summary

Definition of the Need

Interviews

Conceptual PreliminaryDesign

DetailedDesign

Qualitative

Quantitative

Function Allocation

Questionnaires

Focus Groups Prototypes

Anthropometrics

Heuristics

Cognitive WalkthroughTask Analysis

Guidelines

|Q.F.D.

Empirical Analysis - DV&V,Clinical Field Studies

Functional Models

Copyright 2000 by Dr. Craig M. Harvey, Wright State University Dr. Craig Harvey 1 User Centered...

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