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Product Desirability

Social AcceptabilityPractical Acceptability

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Social Acceptability

Social norms applicable at the time– Bermuda shorts and stonewashed jeans– KBC and Packman– Pokemon

– Auto-rickshaw as a family vehicle– Non-branded products– E-invitation for a wedding

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Practical Acceptability

CostUsefulnessCompatibilityReliabilitySupport etc.

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Usefulness

Utility Usability

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Usefulness

Utility – Can the functionality of the product in

principle do what it is supposed to do– Does an educational product teach?– Does an entertainment product entertain?– Does a communications product

communicate?

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Usefulness

Usability– The extent to which a targeted user can

effectively utilize the functionality– Applies to all aspects of a system with which a

human might interface

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Desirable

SociallyAcceptable

Utility

Usable

OtherwisePracticallyAcceptable

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Game

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Clues

1. Is equipped with an internal combustion engine - pass

2. Is available in yellow, black, and yellow and black combo

3. Has three wheels - pass4. Has a parking brake and a foot brake5. Has a 3-speed forward and reverse gear box

- pass6. Levels uneven surfaces nicely and quickly7. Blast weights can be added to level different

types of surfaces - pass

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Answer

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Answer

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Clues

1. Is equipped with an internal combustion engine

2. Is available in yellow, black, and yellow and black combo

3. Has three wheels4. Has a parking brake and a foot brake5. Has a 3-speed forward and reverse gear

box6. Levels uneven surfaces nicely and quickly7. Blast weights can be added to level

different types of surfaces

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Categories of Usability Goals

LearnabilityEase of useSpeed of useError-free useRetention over timeSubjective satisfaction

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Learnability

Learnability goals are the most fundamental usability goals

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Learnability…

Novice users – First-time usability of the product– “Tourists should be able to find out the number of

the bus they need to take.”– “First year students should be able to register

without help.”Advanced beginners / competent performers

– Ease to learn more features – Ease to improve conceptual models – “Regular customers should learn to use the one-

click feature.”– “Daily customers should be able to order

vegetables on their cell phones.”

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Learnability…

First version– All users start out being novices– Have no knowledge of the product– “Recognize terms used in the interface.”

Subsequent versions– Users will transfer existing knowledge– Users will have to learn the differences– “Be 100% backward compatible with these

tasks…”– “Users should notice the new wizard.”

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Example Questions

How quickly can a novice user start using the product?

How quickly can a novice user become an advanced beginner and an advanced beginner become a competent performer?

How much of training and practice is necessary?

Is the user encouraged to explore the product?

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Example Learnability Goals?

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Ease of Use

Define tasks a given user must be able to do– “All advanced beginners should be able to

find and replace text.”Define a preferred method of doing things

– “All competent performers should be able to do a find operation on multiple documents with one command rather than opening each file separately.”

Avoidable tasks– “Users need not write anything on the deposit

envelope.”

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Example Questions

How many users can perform the tasks that they are supposed to?

How many tasks do users need to do that are avoidable?

How easy is it for a group of users to work together?

How easily does the product fit in the users’ current conceptual model?

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Example Ease of Use Goals?

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Speed of Use

Time taken– “It should take a farmer less than five minutes

to identify a transporter.”Number of steps

– “A novice user should be able to deposit cash at the ATM in 3 steps.”

– “Regular commuters should be able to tell time to the next bus without clicking.”

Same as ease of use?

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Example Questions

How long does it take for the user to carry out benchmark set of tasks?

How many steps are involved in a routine task?

How long does it take for users to recover from errors?

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Example Speed of Use Goals?

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Error-free Use

Error – An action of the user that does not accomplish

the desired goalError Rate of a product

– Number of errors made by users while performing benchmark tasks

– Percentage of users who make an error while doing a task

Severity of Errors– The more difficult it is to recover from the

error, more sever it is

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Error-free Use

Limits for error rate of the product – “Should be able to identify himself without errors”

Limits for severity of the errors (catastrophic, major, minor)– “It should be impossible for transporters to loose

data.”– “Prevent users from entering more amount than

they can withdraw.”Ability of users to recognize errors

– “Error messages should not be confused with other messages.”

Ability of users to recover from errors

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Example Questions

How many and what kind of errors are made by users to carry out benchmark tasks?

How many errors do users make repeatedly? How long does it take for the users to

identify the error condition? How forgiving is the interface? What

percentage of errors can users recover from? How many users can identify the cause of

the error and the method of recovering from errors?

How long does it take for users to recover from errors?

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Example Error-free Use Goals?

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Retention Over Time

Most advanced beginners are intermittent users

Don’t have to learn the system from scratchThey just need to remember how to use the

system based on their previous experienceParts of the interface that are used

intermittently– Installation programs– Backup – Restore

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Retention Over Time…

Retention is rarely tested– A product that is easy to learn is considered

to be easy to retain– Define goals are for guiding design

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Example Questions

How much of the interface can a user recall after pre-determined amount of time (hours, days, months, years)?

With how much effort and time can a user re-learn what he has forgotten?

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Example Retention Goals?

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Subjective Satisfaction

Expectations of pleasantness– Derived from life goals and experience goals

of usersSignificantly influence the desirability Important for non-work products

– Home computing, games, fiction Important for niche markets

– Hasselblad for photographers– Apple Mac for designers– Manual blood pressure meter for doctors

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Example Questions

How much did the users enjoy using the product?

Is it “value for money” or is it “hassle free trip”?

What are the cultural issues that matter?How do users rate the product over

competition?

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Example Satisfaction Goals?

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Usability Goals

LearnabilityEase of useError-free useSpeed of useRetention over timeSubjective satisfaction

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Goal Driven Design

Goals drive design– Help speed up design

process– Make design activity

tangible– Help evaluate design

Set goals before design!!!

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You Can’t Meet All Goals

Life critical systems– Railway signals, ATC, operation theatre,

water supply– Reliability, error free use, long training

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You Can’t Meet All Goals

Life critical systems Industrial and commercial uses

– Banks, railway reservation, inventory– Speed of use, minimal training, operator

fatigue and burnout

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You Can’t Meet All Goals

Life critical systems Industrial and commercial usesHome, office, public places

– Office products, ATMs, cell phones– Some tasks with zero learning, encourage self

learning and exploration, support wide range of users (A/NB/CP), subjective satisfaction

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You Can’t Meet All Goals

Life critical systems Industrial and commercial usesHome, office, public placesExploratory and creative

– Architecture, graphic design, product design, audio studio, GIS / GPS / MIS

– Ease of use, some training, encourage self learning and exploration

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You Can’t Meet All Goals

Life critical systems Industrial and commercial usesHome, office, public placesExploratory and creativeCooperative work

– Chat, mailing lists, DLP– Some tasks with zero learning, ease of use,

encourage self learning and exploration, support wide range of users (A/NB/CP), subjective satisfaction

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You Can’t Meet All Goals

Life critical systems Industrial and commercial usesHome, office, public placesExploratory and creativeCooperative workMicro interface

– Hardware, Devnagari keyboard, new paradigm

– Demonstrate new concept, attract early adaptors, zero learnability, ease of use

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Universal Usability (cont.)

Cultural and international diversity– Characters, numerals, special characters, and diacriticals – Left-to-right versus right-to-left versus vertical input and

reading – Date and time formats – Numeric and currency formats – Weights and measures – Telephone numbers and addresses – Names and titles (Mr., Ms., Mme.) – Social-security, national identification, and passport

numbers – Capitalization and punctuation – Sorting sequences – Icons, buttons, colors – Pluralization, grammar, spelling – Etiquette, policies, tone, formality, metaphors

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Universal Usability (cont.)

Users with disabilities– Designers must plan early to

accommodate users with disabilities – Early planning is more cost efficient than

adding on later – Businesses must comply with the

"Americans With Disabilities" Act for some applications

Elderly Users– Including the elderly is fairly ease,

designers should allow for variability within their applications via settings for sound, color, brightness, font sizes, etc.

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Goals for our profession

Potential research topics– Reducing anxiety and fear of computer

usage – Graceful Evolution – Specification and implementation of

interaction – Direct manipulation – Input devices – Online assistance – Information exploration

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Goals for our profession (cont.)

Providing tools, techniques, and knowledge for system implementers– Rapid prototyping is easy when using

contemporary tools – Use general or self-determined guideline

documents written for specific audiences – To refine systems, use feedback from individual

or groups of users Raising the computer consciousness of the general

public– Many novice users are fearful due to experience

with poor product design, – Good designs help novices through these fears by

being clear, competent, and nonthreatening