usability to human-computer interaction

8/14/2019 Usability to Human-Computer Interaction

1/45

1

USABILITY


2/45

Learning Objectives

1) Define usability.2) List the importance of usability.

3) Explain the attributes to usable system.

4) Define usability engineering.

By the end of the lecture, you should be able to:


3/45

3

Create user interface software that you

can maintain well, that is truly object-

oriented, and that allows changes to parts

without impacting everything

Create user interfaces that people can

actually use


4/45

What is Usability?

The effectiveness and efficiency of

the user interface and the users

reaction to that interface.


5/45

What is Usability?Ease of learning

Ease of use

Ease of remembering

Subjective satisfaction

Efficiency of use

Effectiveness of use


6/45

Usability Goal

Promote communication between humans and

computers.

Make this communication doable or easy.

(User Friendly)


7/45

The current state of e-commerce


8/458

Shackles Approach (1990)

For a system to be usable it has to achieve

defined levels on the following scales:

- Effectiveness: performance in accomplishment of

tasks.

- Learnability: degree of learning to accomplish tasks.- Flexibility: adaptation to variation in tasks.

- Attitude: user satisfaction with the system.

What is Usability ?


9/459

What is Usability ?

Nielsen (1993) noted that usability

applies to all aspects of a system with

which a human might interact,including installation and maintenance

procedures.


10/4510

Definition of usability

a measure of the ease with which a

system can be learnedandused, itssafety, effectivenessand efficiency, and

attitude of its userstowards it (Preece et

al., 1994)


11/4511

What to Do With Usability?

Once we have a definition of usability, we

would like to do something:

Demonstrate or evaluate existing systemsDevelop systems with a goal of usability


12/45

Types of Usability Problems

Product doesnt match job or task

Poor organization/layout

Unexpected occurrence of events

Product not self-evidentRequires recall rather than recognition

Inconsistent screens, messages, terminology

Design is inefficient

Cluttered or unattractive designNo feedback or poor feedback about status or errors

No exit or undo

Help or documentation is not helpful


13/4513

Problem

Programmers and users do not talk the same

language..


14/4514

Problem


language..


15/4515

1.1 Illustrating Example

Problem


language..
http://localhost/var/www/apps/conversion/tmp/scratch_1/Macintosh%20HD/Desktop%20Folder/Olga/Colleges/UI%20design/DMS%20example/example.ppthttp://localhost/var/www/apps/conversion/tmp/scratch_1/Macintosh%20HD/Desktop%20Folder/Olga/Colleges/UI%20design/DMS%20example/example.ppt


16/4516

Is this a usable system?


17/4517

Is this a usable error

message?


18/45


19/4519


20/45


21/45


22/45


23/45

Some usability principles

NavigationI can find my way around

FunctionalityI can do what I need to

ControlIm in charge

LanguageI understand the terminology

Help & supportI can get help when I need it

FeedbackI know what the system is doing

ConsistencyI dont have to learn new tricksErrorsMistakes are hard to make, easy to correct

Visual clarityI can recognize things and the design is

clear and appealing.


24/45

24

The Importance of incorporating

usability

When computers were first introduced,

users were limited to computer

professionals or specialists. Now, the usersare much more diverse.

Companies have been adding more features

and functionalities to their products to

attract users, making the products more

complicated.


25/45

25

Importance (contd)

If consumers dont find a product usable, it

may be abandoned.

Usability plays a big factor in thecompetitiveness of products.

Evaluating usability allows manufacturers

to see how the product is doing in themarket.


26/45

Ten Golden Usability RulesA great set of guidelines created by JakobNielsen in his book Usability Engineering.

1. Use simple and natural dialog/language.User interfaces should be simplified as much aspossible, since every additional feature or itemof information on a screen is one more thing to

learn, one more thing to misunderstand, andone more thing to search through. And the GUIshould not overdo it with colour (= Less is more).


27/45

Ten Golden Usability Rules2. Use language that fits the user group.

The language should be based on userslanguage and not on the system-orientedterms. Translation from one language toanother is more than just words. Time,currency, phrases, metaphors, measurements,etc. must fit the culture of the user group.


28/45

Ten Golden Usability Rules3. Minimise the load on short-term memory.

Users should not have to remember informationfrom one part of the dialogue to another.Instructions to the use of the system should bevisible or easily retrievable wheneverappropriate.


29/45

Ten Golden Usability Rules4. Make the graphical user interface coherentand consistent.

The same action should always have the sameeffect. Users will feel confident in using thesystem, and they will be encouraged to try outexploratory learning because they already havepart of the knowledge needed to operate new

parts of the system.


30/45

Ten Golden Usability Rules5. Give the ability to use shortcuts.

Accelerators unseen by the novices mayoften speed up the interaction for the expertsusers, such as: function keys, command keys,macros, etc.


31/45

Ten Golden Usability Rules6. Give feedback to the user s actions.

The system should always keep users informedabout what is going on, through appropriate

feedback within reasonable time i.e.0.1 seconds user feels the system is responding immediately;

1 s. is about the limit users flow of thought will stayinterrupted;

10 seconds is about the limit to keep users attention focusedon the dialogue; so if the user has to wait longer the systemshould give feedback about the waiting time.

Warning messages should be used when theuser is going to perform an irreversible action.


32/45

Ten Golden Usability Rules7. Avoid error situations.

Ask the user if s/he really wants to do theaction especially if the action leads to serious

consequences. Avoid having too similarcommands in the interface.

Commands whose actions are oppositeshould not be placed close to each other.


33/45

Ten Golden Usability Rules8. Give clear exit marks.

Users often choose actions by mistakeand will need a clearly marked emergency

exitto leave the unwanted state withouthaving to go through an extended dialogue.Cancel should be offered when the operationwill take a long time. In the navigation bars, the

users should be able to back up.


34/45

Ten Golden Usability Rules9. Give clear and understandable errormessages.Simple rules for error messages:

should be phrased clearly and avoid obscure codesmessages should be precise, not vague or general

messages should constructively help the user tosolve the problem

messages should be polite and not intimidate theuser or put the blame explicitly on the userILLEGAL, FATAL ACTION, JOB ABORTED!phrases should not be used.


35/45

Ten Golden Usability Rules10. Give clear help and understandable

documentation.Information should be easy to search, it

should be focused on the users task. List the

concrete steps that should be carried out. The

help manual should not be too large.


36/45

Golden Rules for d UIsInteresting and amusing reading

from the SAP Design Guild:

http://www.sapdesignguild.org/com

munity/design/golden_rules.asp
http://www.sapdesignguild.org/community/design/golden_rules.asphttp://www.sapdesignguild.org/community/design/golden_rules.asphttp://www.sapdesignguild.org/community/design/golden_rules.asphttp://www.sapdesignguild.org/community/design/golden_rules.asp


37/45

37

Usability Engineering

A set of activities that ideally take place

throughout the lifecycle of the product,

with significant activities happening inthe early stages before the user interface

has even been designed


38/45

38

Usability Engineering Process


39/45

39

Usability Engineering Vs Usability

Usability engineering

Methodical approach to producing user interface

A way to deliver a product that works

Usability

Attribute to usable system

Principles of Usability


40/45


41/45

Summary

Usability Metricsmeasures collected for describing usability of system

Usability Testingassessment of usability of system, in terms of learnability,

ease of use, flexibly, safety, effectiveness, efficiency, and

attitude of users to system

Usability Labsspecial purpose labs for conducting studies, video & audio

facilities, observation of "subjects" ....


42/45

42


43/45

ExerciseChoose any website

Evaluateyour GUI for your web-site

(consider the usability principles).

Perform your measurements, interviews,observations, etc.

Summarize what you have learned in terms

of usability principles.Redesign your original web-site concept.

State how your design has changed as a

result of the testing.


44/45

Types of Usability Problems

Product doesnt match job or task

Poor organization/layout

Unexpected occurrence of events

Product not self-evidentRequires recall rather than recognition

Inconsistent screens, messages, terminology

Design is inefficient

Cluttered or unattractive designNo feedback or poor feedback about status or errors

No exit or undo

Help or documentation is not helpful


45/45

Exercises

Define the concept of usability and usability

engineering.

Explain TWO (2)user interface designguidelines to support usability.

Discuss how learnability and memorability

principles support usability for wordprocessing.

[indicate how these principles have been

applied for HCI]

usability to human-computer interaction

Documents