Ch 3 Interaction Design Process

Yonglei Tao

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Interaction Design An iterative process

through cycles of design-evaluation-redesign

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User-Centered Design (UCD) Pioneered by Donald Norman’s research

lab at UC San Diego A design framework for building usable

systems Principles Techniques

User-Centered Design (UCD) Design should emerge from the user’s

Tasks – data, functions, and workflows Goals Environment

Focus on human-centric issues Cognition Perception Physical attributes and conditions

Characteristics Early focus on users and their tasks Continuous evaluations to determine ease

of learning and ease of use Iterative design

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User-Centered Design Involving the following methods

User Participation Focus Groups Questionnaires Observations Walkthroughs Expert Evaluations Usability Testing

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Interaction Design Models Waterfall Model Spiral Model Dynamic Systems Development Method Prototype-Based Models Discount Usability Engineering Contextual Inquiry

Waterfall Model

A Modified Model

Discount Usability Engineering Proposed by Jakob Nielsen Basic ideas

Changes in user interface design are substantial in the early stages of development

No need to use comprehensive prototyping and usability testing techniques

Benefits derived from even small amounts of user testing would have a significant impact on the usability of the design

So “test early and often”

User Testing Problems that can be identified from a

usability test with n users can be described as follows

Basic Techniques Scenarios

Paper prototyping on the basis of scenarios Thinking aloud

Involve 3 to 6 users for usability testing Ask them to think out loud when performing

given tasks Collect data by note-taking

Heuristic evaluation Evaluate according to established usability

principles Involve a few reviewers to avoid personal bias Do early in the design process

Cost Savings in a Medium Project

Source - http://www.nngroup.com/articles/guerrilla-hci/

How Many Users in a Test? Test five users (Jakob Nielsen, 2012)

Allowing you to find almost as many usability problems as you would find using many more test users

Sufficient to collect insights to drive your design There are exceptions

Quantitative studies – test at least 20 users Card sorting – test at least 15 users Eyetracking – test 39 users for stable heatmaps

A small number of test users are more cost effective

More tests, not more users in each test

83 Case Studies by Norman Group

Source - http://www.nngroup.com/articles/how-many-test-users/