lecture 2: usability

CMSC 434 Introduction to Human Computer Interaction Spring 2010 1

Lecture 2: Usability

January 27

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What is Usability?

•  How easy is it for users to perform a particular task using a system or device?

•  How well a system or device can support the users to perform a particular task?

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Usability of doors

1.  Why do door knobs always turn the same direction to open?

2.  Why do door knobs installed at waist height? 3.  Why do some people rather use a small side

door next to a large revolving door? 4.  Why do some doors have knobs, some bars? 5.  Why do doors have dampers and closers? 6.  Why do doors have see through windows? 7.  Why do doors lock only from outside with keys? 8.  Why do people decorate doors?

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Five attributes of usability

•  Easy to learn •  Efficient to use •  Easy to remember •  Few user errors •  Subjectively pleasing

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Five attributes of usability

•  Easy to learn •  Efficient to use •  Easy to remember •  Few user errors •  Subjectively pleasing

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Three aspects of HCI

•  Design •  Evaluation •  Implementation

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1. Easy to learn

•  Evaluation – Can users learn to perform the correct

interactions?

•  Design – How can we provide the right guidance to

help users learn the interactions easily?

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2. Efficient to use

•  Evaluation – How fast can users perform the correct

interactions?

•  Design – How can we optimize the interface design

for faster interactions?

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3. Easy to remember

•  Evaluation – Can users remember the correct

interactions?

•  Design – What reminders can we provide to help

users remember the correct interactions?

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4. Few user errors

•  Evaluation –  Is it likely or unlikely for users to make

interaction errors by accident?

•  Design – How can we identify and eliminate design

elements prone to user accidents?

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5. Subjectively pleasing

•  Evaluation – Are users pleased with the way they interact

with the system?

•  Design – How do we introduce design features to

reduce stress and increase satisfaction?

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People complain about usability problems

Real users’ complaints about VLC Player (1/2) •  Hard-to-guess shortcuts to operate with the

movie. •  Non-responsive shortcuts in WX interface. •  Unresponsive stop/play. •  Preferences are way too big. You can navigate

thru them all the day long and you won't find what you're really looking for.

(cont…)

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People complain about usability problems

Real users’ complaints about VLC Player (2/2) •  Hard to remember what filters have been

enabled. •  Adding/removing a video filter during

playback often causes video window to resize.

•  The fullscreen mode is always left between two videos, which is annoying when using playlists. It should only be disabled manually.

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Usability Engineering

•  Focus on assessing and making recommendations to improve usability

•  Research and design process that ensures a product with good usability

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Benefits of usability engineering to companies

•  Increase customer satisfaction •  Increase sales and revenues •  Reduce development time and costs •  Reduce maintenance costs •  Decrease training and support costs

Example: IBM

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A day in life of a usability engineer

Lani Hathway at EA Sports (1/2) •  Interview project team members about

their product, usability concerns, design process

•  Attend team meetings on strategy, feature design, schedule, and other hot topics

•  Help teams set usability goals (cont...)

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A day in life of a usability engineer

Lani Hathway at EA Sports (2/2) •  Drive user research activities such as

gathering data for creating user personas, task lists and scenarios

•  Design usability tests •  Present results from usability tests and

other user research to project teams •  Summarize results from usability tests

into design guidelines or style guides

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Usability is relative to

•  Users •  Tasks •  Locations •  Time

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Five attributes of usability

Usability

Utility

Usefulness Few errors

Memorizability

Learnbility

Efficiency

Satisfaction Practical acceptability

Speed

Security

Reliability

Cost

Size

Social acceptability

System acceptability

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The new iMac •  LED backlighting •  More pixels, better picture •  Stunning from every angle •  Quad-core power •  Revved-up graphics •  More memory and storage •  Built-in Wi-Fi •  Wireless keyboard •  iSight •  The world’s first multi-touch mouse •  Ports for everything •  Wall mountable

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Tradeoffs

•  Usability attributes – Efficient or easy to learn – Efficient or robust to user errors – Easy to learn or easy to remember

•  User groups – Experts or novices

•  Tasks – Reading, typing, coding or drawing

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Activity: Me vs. Users

1.  IDE or Command line? 2.  Default or personalization? 3.  On-access or on-demand virus scan? 4.  Show or hide captions? 5.  Folders or search? 6.  Speed or stamina? 7.  Browser default page?

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What are the usability tradeoffs of these keyboard designs?

Multi-tap Keyboard Slideout Keyboard Touchscreen

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•  Homework: Implementation 1 – Due next Monday (2/1)

•  Micro homework: take a picture of a door – The one you used more often. – The one you think should be fixed.

•  Project: Preferences – Due next Monday (2/1) – Choose from three possible themes

•  Design for improving health •  Design for a special user population •  Redesign a bad website

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Activity: Amazon Reviews