Usability Engineering Dr. Dania Bilal IS 582 Spring 2006

NextPrevious What Is Usability Engineering? Measures multiple components of the user interface Addresses the relationships between system and its users Focuses on the HCI field

NextPrevious What Is Usability Engineering? Bridges the gap between human and machines Measures the quality of a system in relation to its intended users Involves several methods, each applied at appropriate time of the design and development process

NextPrevious Importance of Usability The sooner problems are found, the less expensive it is to fix them –Saves money by reducing designers’ and developers’ time

NextPrevious Importance of Usability Learn more about users, tasks, expectations, successes, failures, information seeking, etc. and take these into consideration in redesigning a system or designing new one

NextPrevious Usability Attributes As described by Neilsen –Learnability –Efficiency –Memorability –Errors & their severity –Subjective satisfaction

NextPreviousLearnability The system must be easy to learn, especially for novice users. –Hard to learn systems are usually designed for expert users. –There is a learning curve for novice and expert users.

NextPreviousEfficiency The 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 learning

NextPreviousMemorability The system should be easy to remember, especially by casual users, so that they do not have to learn it all over again after a period of not using it.

NextPreviousErrors The system should have a low error rate and should provide the user with a recovery mechanism from errors. –Minor errors –Major errors

NextPrevious Minor Errors User was able to recover from them –through system feedback –through awareness of error made Errors that did not greatly slow down the user’s interaction with the system

NextPrevious Major Errors Difficult to recover from them Lead to faulty work especially if they are high in frequency May not be discovered by the user –These errors can be catastrophic

NextPrevious Subjective Satisfaction The system should be likeable by users Satisfaction varies with kind of system used (educational vs. entertainment)

NextPreviousAssumptions 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 help Source: Nielsen, J. (1993). Usability Engineering. San Diego: Morgan Kaufman.

NextPreviousFactors Address the functionality of the system vis-à-vis: –user needs –user tasks –user information seeking –user expectations –user cognitive processes

NextPrevious Usability Testing Part of the process of usability engineering Involves users in the evaluation of a system by testing it Goal –Uncover problems and correct them

NextPrevious Usability Evaluation Conducted at many stages during and after the system design process. Employs various methods

NextPreviousMethods Cognitive walkthrough Focus groups Prototyping Task analysis Inspection User testing

NextPrevious Usability Heuristics c/heuristic_list.html for usability principles c/heuristic_list.html c/heuristic_evaluation.html for how to conduct a heuristic evaluation c/heuristic_evaluation.html

NextPrevious Usability Tests Stages –Preparation –Introduction –Test itself –Debriefing Neilsen, J. (1993). Usability Engineering. San Diego: Morgan Kaufman.

NextPreviousPreparation Preparation for the experiment and data collection –Location of test (e.g., room to be used) –System to be used, capturing software, etc. –Test materials, instructions, questionnaires to be completed, as applicable

NextPreviousIntroduction Test introduction includes –Purpose of the test –Test results to be used to improve interface –Confidentiality of results & IRB –Explanation of software and equipment used to collect data

NextPreviousIntroduction –Users to ask clarifying questions anytime before and during the experiment –Users to report problems and difficulty in using system during experiment (e.g., screen freeze) –Verbal instructions, as applicable Introduction

NextPrevious Running the Test Experimenter(s) should refrain from interacting with users (e.g., personal opinions should not be expressed) Experimenter(s) guide(s) observers. Both groups should refrain from making obtrusive comments during the experiment

NextPreviousDebriefing User is debriefed after the test and may be asked to make comments or suggestions –verbally (via individual interview) –by completing a questionnaire

NextPreviousDebriefing Experimenter ensures that files are collected with correct labeling; checks captured data files, questionnaires, etc. Experimenter may write a brief preliminary report while events are still fresh.