Usability EngineeringPurposesSlide 3Usability AttributesLearnabilityEfficiencyMemorabilityErrorsMinor ErrorsMajor ErrorsSubjective SatisfactionAssumptionsCognitive Walkthrough MethodCognitive Walkthrough MethodSlide 15Sample Questions for WalkthroughCognitive WalkthroughDebriefing SessionWalkthrough ReportHeuristic EvaluationStages of Heuristic EvaluationSlide 22Slide 23Neilsen’s HeuristicsUsability HeuristicsUsability EngineeringDr. Dania BilalIS 588Spring 2007Drs. Bilal & NormorePurposesMeasures multiple components of the user interfaceAddresses relationships between system and its usersBridges the gap between human and machinesPurposesMeasures the quality of system design in relation to its intended usersInvolves several methods, each applied at appropriate time of the design and development processUsability AttributesAs described by NeilsenLearnabilityEfficiencyMemorabilityErrors & their severitySubjective satisfactionLearnabilitySystem must be easy to learn, especially for novice usersHard to learn•systems are usually designed for expert usersLearning curve for novice and expert usersEfficiencySystem should be efficient to use so that once the user has learned how to use it, the user can achieve a high level of productivityEfficiency increases with learningMemorabilitySystem should be easy to remember, especially by casual usersNo need to learn how to use system all over again after a period of not using itErrors System should have a low error rateSystem should provide user with a recovery mechanismMinor errorsMajor errorsMinor ErrorsErrors that did not greatly slow down user’s interaction with the system User is able to recover from themthrough system feedbackthrough awareness of error madeMajor ErrorsDifficult to recover from themLead to faulty work if high in frequencyMay not be discovered by the userErrors can be catastrophicSubjective SatisfactionSystem should be likeable by users (affective)Satisfaction varies with purpose of systemuser goalsAssumptionsThe designer’s best guess is not good enoughThe user is always rightThe user is not always rightUsers are not designersDesigners are not usersMore features are not always betterMinor interface details matterOnline help does not really helpSource: Nielsen, J. (1993). Usability Engineering. San Diego: Morgan Kaufman.Cognitive Walkthrough MethodInvolves experts acting on behalf of actual usersCharacteristics of typical users are identified & documentedTasks focusing on aspects of design to be evaluated are developedCognitive Walkthrough MethodAn observer “experimenter” is presentPrepares tasksTakes notes, Provides help, etc. Coordinates and overseas final reportCognitive Walkthrough MethodExpert walkthrough interface on each taskExpert records problems that user may experienceAssumptions about what would cause problems and why are notedBenchmarks may be used for each taskSample Questions for WalkthroughWill the user know what to do to complete part of or whole task successfully?Can user see button or icon to use for next action?Can user find specific subject category from the hierarchy?Cognitive WalkthroughEach expert documents experience about walkthrough for each taskCritical problems documentedProblems and what cause them are explainedDraft report/notes are compiled and shared with other experts and ExperimenterDebriefing SessionExperts and experimenter meet & discuss findingsExperimenter shares his/her observational notes with expertsFindings include success stories & failure stories, as applicableConsolidated report is generatedWalkthrough ReportInclude questions experts for each of the tasks and the consolidated answer See Text, p. 420 for examples Use benchmarks and map out the finding for each taskSee Assignment 5 for further info.Heuristic EvaluationEvaluators interact with an interface several times and map interface to specific heuristics or guidelinesExample: Nielsen’s ten heuristicsEach evaluator generates a reportReports are aggregated and final report is generatedAn observer may be presentStages of Heuristic Evaluation Stage 1: Debriefing sessionExperts told what to doWritten instructions provided to each expert Heuristics provided to each expert as part of written instructionsVerbal instructions may be includedStages of Heuristic EvaluationStage 2: Evaluation sessionsEach expert tests system based on heuristicsExpert may also use specific tasksTwo passes are taken through interface•First pass: overview and familiarity•Second pass: Focus on specific features & identify usability problemsStages of Heuristic EvaluationStage 3: Debriefing sessionExperts meet to discuss outcome and compare findingsExperts consolidate findingsExperts prioritize usability problems found & suggest solutionsNeilsen’s HeuristicsTen heuristics found athttp://www.useit.com/papers/heuristic/heuristic_list.html & Text, pp. 408-409.Additional rules:See Text, p. 409; pp. 412-417.Some heuristics can be combined under categories and given general description.Usability Heuristicshttp://www.usabilityfirst.com/methods http://www.useit.com/papers/heuristic/heuristic_evaluation.html (how to conduct a heuristic evaluation)http://www.uie.com/articles (collection of articles)http://www.uie.com/articles/usability_tests_learn/ Learning about usability test (Jared Spool)http://www.useit.com/papers/heuristic/severityrating.html (Severity