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Usability 2009 J T Burns 1 Usability & Usability Engineering

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Usability & Usability Engineering. Usability. What is usability Easy to use? User Friendly? A system with a GUI?. How do we build bridges? How do we build skyscrappers?. Usability Engineering. No clear definition until fairly recently First proposed by Shakel 1987 - PowerPoint PPT Presentation

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Page 1: Usability & Usability Engineering

Usability 2009 J T Burns 1

Usability & Usability Engineering

Page 2: Usability & Usability Engineering

Usability 2009 J T Burns 2

Usability What is usability Easy to use? User Friendly? A system with a GUI?

Page 3: Usability & Usability Engineering

How do we build bridges?

How do we build skyscrappers?

Usability 2009 J T Burns 3

Page 4: Usability & Usability Engineering

Usability 2009 J T Burns 4

Usability Engineering

No clear definition until fairly recently First proposed by Shakel 1987 Tried to provide an operational

definition of Usability quantify the “usabilityusability” of a system - no

universal definition of the term

Page 5: Usability & Usability Engineering

Usability 2009 J T Burns 5

Usability Shackle

LEAF specifications take the form of precise

statements of performanceperformance goals. Typically related to

Ease of learning (LearnabilityLearnability) ThroughputThroughput (Efficiency) SubjectiveSubjective matters of user satisfaction (Attitude) Flexibility

Page 6: Usability & Usability Engineering

Usability 2009 J T Burns 6

Usability goals Effective to use Efficient to use Safe to use Have good utility Easy to learn Easy to remember how to use

Page 7: Usability & Usability Engineering

Usability 2009 J T Burns 7

Activity on usability How long should it take and how

long does it actually take to: use a DVD to play a video? use a PVR to record two programs? use an authoring tool to create a

website?

Page 8: Usability & Usability Engineering

Usability 2009 J T Burns 8

User experience goals Satisfying - rewarding Fun - support creativity Enjoyable - emotionally fulfilling Entertaining …and more Helpful Motivating Aesthetically pleasing Motivating

Page 9: Usability & Usability Engineering

Usability 2009 J T Burns 9

Usability and user experience goals How do usability goals differ from

user experience goals? Are there trade-offs between the

two kinds of goals? e.g. can a product be both fun and

safe? How easy is it to measure usability

versus user experience goals?

Page 10: Usability & Usability Engineering

Usability 2009 J T Burns 10

Usability Evaluation Techniques

There are 4 core evaluation paradigms

Quick and Dirty Usability Testing Field Studies Heuristic or predictive evaluation

Page 11: Usability & Usability Engineering

Usability 2009 J T Burns 11

Quick and Dirty Is common practice where designers get

feedback from users or HCI consultants to check there ideas are ok

Can be done at any stage – emphasis is on speed rather than detailed well documented findings – do you like this layout, this icon?

Is used when timescales are short Has become particularly popular in web

design

Page 12: Usability & Usability Engineering

Usability 2009 J T Burns 12

Usability testing Dominant approach in 80’s remains

very important – typically lab based Move towards other forms including

field testing and heuristic evaluations

Testing involves measuring typical users performing real tasks and recording the time taken or number of errors made

Page 13: Usability & Usability Engineering

Usability 2009 J T Burns 13

Usability – Field Tests Field studies of usability are done in the

users natural setting Aims to determine what the user

actually does and what other elements may impact on the interaction with the device or system

Field studies can be used to Identify opportunities for new products Determine requirements for design

Page 14: Usability & Usability Engineering

Usability 2009 J T Burns 14

How might you undertake an evaluation of a family using an innovative home entertainment system that gave them wi-fi access throughout the home with access to the internet, video on demand, PVR programming, games etc?

What would you want to evaluate?

Page 15: Usability & Usability Engineering

Usability 2009 J T Burns 15

Usability testing Recording of users performance may be

through a number of techniques including Video recording Direct observation Software logging

Resulting data is used to inform the design and engineer it to meet the desired performance levels – usability engineering

Page 16: Usability & Usability Engineering

Usability 2009 J T Burns 16

Usability principles/heuristics Similar to design principles, except

more prescriptive Used mainly as the basis for

evaluating systems Provide a framework for heuristic

evaluation Experts guided by heuristics to

predict usability problems

Page 17: Usability & Usability Engineering

Usability 2009 J T Burns 17

Usability specifications

Whiteside et al proposed that usability could be measured in terms of attributes which can be measured

Important because they offer a way of incorporating usability into software quality assurance specifications

Example (of a data retrieval system) “90% of all users will be able to

identify the location of a book in the library by its shelf number, given the author’s name and book title, within ten seconds...”

Page 18: Usability & Usability Engineering

Usability 2009 J T Burns 18

Objective of usability specifications To make decisions about user interface goals

explicit Support effective collaboration within the design

team, between its members Usability specification becomes part of the

general requirements specification Is an essential and integral part of UCD

Can be used to resolve conflict between,for example, users, analysts and designers over parts of the design

Can help determine whether need for further iterations and prototyping

Page 19: Usability & Usability Engineering

Usability 2009 J T Burns 19

Usability Attributes Attributes should be measurable Example Attributes include

Time to complete a task % of task completed Number or % of errors made % of users who like the design No of times user asks for help/gets lost

Page 20: Usability & Usability Engineering

Usability 2009 J T Burns 20

Components of a usability specification

Statement of the usability goal Statement of the usability attributeusability attribute Statement of the criteriacriteria which will represent

attainment of the specification Now level Worst case Planned level Best case

Statement of which set or subset of usersusers the specification applies to

A statement of preconditionspreconditions for the measurement

Page 21: Usability & Usability Engineering

Usability 2009 J T Burns 21

Sample specification

Usability Goal: Users can quickly obtain a balance from an ATM Attribute: Time Measuring method: Observe and record

Time taken by users to obtain balance Now level: 30 secs Worst case: 25 secs Planned level: 20 secs Best case: 15 User class: All Preconditions: Users are familiar with ATMs

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Usability 2009 J T Burns 22

Usability Specification Provide an alternative usability

specification using a different attribute that could determine whether the stated goal had been achieved

Page 23: Usability & Usability Engineering

Usability 2009 J T Burns 23

Usability Specifications Create a usability specification for

the following devices/systems A web site selling books An MP3 player A airline reservation system A self service check in system

Page 24: Usability & Usability Engineering

Usability 2009 J T Burns 24

Some attributes you may have thought of:

No of clicks Time No of errors Time to learn % who remember functions/meaning

of icons % Can use 1st time

Page 25: Usability & Usability Engineering

Usability 2009 J T Burns 25

Usability principles (Nielsen 2001)

Visibility of system status Match between system and the real world User control and freedom Consistency and standards Help users recognize, diagnose and recover from

errors Error prevention Recognition rather than recall Flexibility and efficiency of use Aesthetic and minimalist design Help and documentation

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Usability 2009 J T Burns 26

Problems with UE Assertion of clear measurable criteria Measures specific user actions in

specific situations Other factors may contribute to overall

performance Setting appropriate criteria

Important to look for ‘now’ level

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Usability 2009 J T Burns 27

Further Reading www.useit.com

This is the usability site of Jacob Nielsen