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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  • Usability 2009 J T Burns*Usability & Usability Engineering

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*UsabilityWhat is usabilityEasy to use?User Friendly?A system with a GUI?

    Usability 2009 J T Burns

  • How do we build bridges?

    How do we build skyscrappers?Usability 2009 J T Burns*

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability EngineeringNo clear definition until fairly recentlyFirst proposed by Shakel 1987Tried to provide an operational definition of Usability quantify the usability of a system - no universal definition of the term

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability ShackleLEAFspecifications take the form of precise statements of performance goals. Typically related toEase of learning (Learnability)Throughput (Efficiency)Subjective matters of user satisfaction (Attitude)Flexibility

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability goalsEffective to useEfficient to useSafe to useHave good utilityEasy to learnEasy to remember how to use

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Activity on usabilityHow 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?

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*User experience goalsSatisfying- rewardingFun- support creativityEnjoyable- emotionally fulfillingEntertainingand moreHelpfulMotivatingAesthetically pleasingMotivating

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*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?

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability Evaluation TechniquesThere are 4 core evaluation paradigmsQuick and DirtyUsability TestingField StudiesHeuristic or predictive evaluation

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Quick and DirtyIs common practice where designers get feedback from users or HCI consultants to check there ideas are okCan 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 shortHas become particularly popular in web design

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability testingDominant approach in 80s remains very important typically lab basedMove 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

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability Field TestsField 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 systemField studies can be used toIdentify opportunities for new productsDetermine requirements for design

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*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?

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability testingRecording of users performance may be through a number of techniques includingVideo recordingDirect observationSoftware loggingResulting data is used to inform the design and engineer it to meet the desired performance levels usability engineering

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability principles/heuristicsSimilar to design principles, except more prescriptiveUsed mainly as the basis for evaluating systemsProvide a framework for heuristic evaluationExperts guided by heuristics to predict usability problems

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability specificationsWhiteside et al proposed that usability could be measured in terms of attributes which can be measuredImportant because they offer a way of incorporating usability into software quality assurance specificationsExample (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 authors name and book title, within ten seconds...

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Objective of usability specificationsTo make decisions about user interface goals explicitSupport effective collaboration within the design team, between its membersUsability specification becomes part of the general requirements specificationIs an essential and integral part of UCDCan be used to resolve conflict between,for example, users, analysts and designers over parts of the designCan help determine whether need for further iterations and prototyping

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability AttributesAttributes should be measurableExample Attributes includeTime to complete a task% of task completedNumber or % of errors made% of users who like the designNo of times user asks for help/gets lost

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Components of a usability specification

    Statement of the usability goalStatement of the usability attributeStatement of the criteria which will represent attainment of the specificationNow levelWorst casePlanned levelBest caseStatement of which set or subset of users the specification applies toA statement of preconditions for the measurement

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Sample specification

    Usability Goal: Users can quickly obtain a balance from an ATMAttribute: TimeMeasuring method: Observe and record Time taken by users to obtain balance Now level: 30 secsWorst case: 25 secsPlanned level: 20 secsBest case: 15User class: AllPreconditions: Users are familiar with ATMs

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability SpecificationProvide an alternative usability specification using a different attribute that could determine whether the stated goal had been achieved

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability SpecificationsCreate a usability specification for the following devices/systemsA web site selling booksAn MP3 playerA airline reservation systemA self service check in system

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Some attributes you may have thought of:No of clicksTimeNo of errorsTime to learn% who remember functions/meaning of icons% Can use 1st time

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Usability principles (Nielsen 2001)Visibility of system statusMatch between system and the real worldUser control and freedomConsistency and standardsHelp users recognize, diagnose and recover from errorsError preventionRecognition rather than recallFlexibility and efficiency of useAesthetic and minimalist designHelp and documentation

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Problems with UEAssertion of clear measurable criteriaMeasures specific user actions in specific situationsOther factors may contribute to overall performanceSetting appropriate criteriaImportant to look for now level

    Usability 2009 J T Burns

  • Usability 2009 J T Burns*Further Readingwww.useit.com

    This is the usability site of Jacob Nielsen

    Usability 2009 J T Burns