Transcript Nielsen Chapter 4

Prioritizing Web Usability
Nielsen and Loranger
Chapter 4: Prioritizing Your Usability
Problems
Paul Ammann
http://cs.gmu.edu/~pammann/
SWE 432
Design and Implementation of Software for the Web
Overview
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What Makes Problems Severe
The Scale of Misery
Why Users Fail
Is it Enough to Focus on the Worst Problems?
Fixing the Web, Starting With The Worst Problems
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How Severe Is The Problem?
• High Severity Problems Impose an Unacceptable Cost
and/or Loss of Business:
– Prevents Use of Site
– Actively Drives Users Away:
• Dime Savings Bank (See Investor Relations)
• Medium Severity Problems Cause
– Confusion, Frustration, Some Lost Business
• Low Severity Problems: California State Parks
– Cosmetic and Irritating
– But Do Not Individually Hurt Business
A Rough and Ready Triage Approach
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Example: Usability For Hospital OrderEntry System
• Dosage Listed in “Units of Medication”, i.e. Pills.
– Subtle Message: One Pill = One Typical Dose
– Solution: Interface Should List Typical Dosage
• Changes To Medication Dosage
– If Old Order Not Cancelled, Patient Gets Sum of Medications
– Similar to Double Debit In Online Bill Pay
• Moral: Always Check for Apparent Duplicate Requests
• Memory Overload: Each Patient Had Up To 20 Screens
– Way Past the 7 +/- 2 Memory Limit
– Staff Resorted to Paper Notes, With Data Entry At Shift End
• Moral: Sticky Notes Are a Bad Sign!
Usability Matters
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What Makes Problems Severe
• Frequency
– How Many Users Will Encounter The Problem?
• Impact
– How Much Trouble Does Problem Cause To Users Who Do
Encounter It?
• Persistence
– One-Off Problems That Users “Figure Out”
• Example: Login
– Repeated Trouble
• Persistent Confusion
• Note: Persistently Abused Users Eventually Just Leave
How Often? How Much? How Long?
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The Scale of Misery
• Scale of Misery
• Usability Problems Are Weighted By Severity Score
• Note Huge Proportion Of Misery In Basic Functions:
– Finding Information
– Reading Information
– Understanding Information
• Roughly 37% of Difficulties in Getting to Right Page
• Roughly 62% of Difficulties At Page Level
– Bad Page or Page Progression Design
Surprisingly, This is Still Legal
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Why Users Fail
• Why Users Fail
• Problems That Cause A User to Leave, Give Up, Or
Mess Up
• Search and IA are Large Factors in Task Failure
– You Can’t Succeed If You Can’t Find It
• Readability Less of A Factor
– You Can Succeed, Even If You Are Annoyed
Bottom Line: Search, Findability, Actual Info on Page
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Is it Enough to Focus on the Worst
Problems?
• Even Minor Problems Can Eventually Drive Users
Away
• Next Chapters Focus On Key Areas:
– Search
– Navigation
– Readability
Understanding How To Help Users Succeed
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