류 현 정류 현 정 Human Computer Interaction Introducing evaluation

The aims  Discuss how developers cope with real- world constraints  Explain the concepts and terms used to discuss evaluation  Examine how different techniques are used at different stages of development

Two main types of evaluation  Formative evaluation is done at different stages of development to check that the product meets users ’ needs  Summative evaluation assesses the quality of a finished product  Our focus is on formative evaluation

What to evaluate  Iterative design & evaluation is a continuous process that examines:  Early ideas for conceptual model  Early prototypes of the new system  Later, more complete prototypes  Designers need to check that they understand users ’ requirements

Bruce Tognazzini tells you why you need to evaluate  “ Iterative design, with its repeating cycle of design and testing, is the only validated methodology in existence that will consistently produce successful results. If you don ’ t have user-testing as an integral part of your design process you are going to throw buckets of money down the drain. ”  See AskTog.com for topical discussion about design and evaluation

When to evaluate  Throughout design  From the first descriptions, sketches etc. of users needs through to the final product  Design proceeds through iterative cycles of ‘ design-test-redesign ’  Evaluation is a key ingredient for a successful design

Approaches: Naturalistic  Naturalistic:  describes an ongoing process as it evolves over time  observation occurs in realistic setting  ecologically valid  “ real life ”  External validity  degree to which research results applies to real situations

Approaches: Experimental  Experimental  study relations by manipulating one or more independent variables  experimenter controls all environmental factors  observe effect on one or more dependent variables  Internal validity  confidence that we have in our explanation of experimental results  Trade-off: Natural vs Experimental  precision and direct control over experimental design versus  desire for maximum generalizability in real life situations

Approaches: Reliability Concerns  Would the same results be achieved if the test were repeated?  Problem: individual differences:  best user 10x faster than slowest  best 25% of users ~2x faster than slowest 25%  Partial Solution  reasonable number and range of users tested  statistics provide confidence intervals of test results  95% confident that mean time to perform task X is 4.5+/-0.2 minutes means 95% chance true mean is between 4.3 and 4.7, 5% chance its outside that

Approaches: Validity Concerns  Does the test measure something of relevance to usability of real products in real use outside of lab?  Some typical reliability problems of testing vs real use  non-typical users tested  tasks are not typical tasks  physical environment different  quiet lab vs very noisy open offices vs interruptions  social influences different  motivation towards experimenter vs motivation towards boss  Partial Solution  use real users  tasks from task-centered system design  environment similar to real situation

Qualitative Evaluation Techniques

Qualitative methods for usability evaluation  Qualitative:  produces a description, usually in non-numeric terms  may be subjective  Methods  Introspection  Extracting the conceptual model  Direct observation  simple observation  think-aloud  constructive interaction  Query via interviews and questionnaires  Continuous evaluation via user feedback and field studies

Querying Users via Interviews  Excellent for pursuing specific issues  vary questions to suit the context  probe more deeply on interesting issues as they arise  good for exploratory studies via open-ended questioning  often leads to specific constructive suggestions  Problems:  accounts are subjective  time consuming  evaluator can easily bias the interview  prone to rationalization of events/thoughts by user  user ’ s reconstruction may be wrong

Evaluating the 1984 OMS  Early tests of printed scenarios & user guides  Early simulations of telephone keypad  An Olympian joined team to provide feedback  Interviews & demos with Olympians outside US  Overseas interface tests with friends and family.  Free coffee and donut tests  Usability tests with 100 participants.  A ‘ try to destroy it ’ test  Pre-Olympic field-test at an international event  Reliability of the system with heavy traffic

Development of HutchWorld  Many informal meetings with patients, carers & medical staff early in design  Early prototype was informally tested on site  Designers learned a lot e.g.  language of designers & users was different  asynchronous communication was also needed  Redesigned to produce the portal version

Usability testing  User tasks investigated:  how users ’ identify was represented  communication  information searching  entertainment  User satisfaction questionnaire  Triangulation to get different perspectives

Findings from the usability test  The back button didn’t always work  Users didn’t pay attention to navigation buttons  Users expected all objects in the 3-D view to be clickable  Users did not realize that there could be others in the 3-D world with whom to chat  Users tried to chat to the participant list

Key points  Evaluation & design are closely integrated in user-centered design  Some of the same techniques are used in evaluation & requirements but they are used differently (e.g., interviews & questionnaires)  Triangulation involves using a combination of techniques to gain different perspectives  Dealing with constraints is an important skill for evaluators to develop