Transcript Ch 4 (pptx)
Prioritizing Web Usability Nielsen & Loranger : Chapter 4 Prioritizing Your Usability Problems Jeff Offutt http://www.cs.gmu.edu/~offutt/ SWE 432 Design and Implementation of Software for the Web Usability Can Be Life Or Death In war, a usability flaw can lead to a deadly halfsecond delay by a fighter pilot In 1979, a usability problem contributed to the 3 Mile Island nuclear plant accident 1 July 2016 © Offutt 2 Overview / Chapter 4 Outline 1. 2. 3. 4. What Makes Problems Severe The Scale of Misery Why Users Fail Is it Enough to Focus on the Worse Problems ? We cannot fix every problem How do we prioritize? 1 July 2016 © Offutt 3 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 example from book has been fixed! • Medium severity problems cause – Confusion, frustration, some lost business • Low severity problems – Cosmetic and irritating – But do not individually hurt business – California state parks example from book has been fixed! Must balance severity with effort to fix 1 July 2016 © Offutt 4 What Makes Problems Severe • Frequency – How many users will encounter the problem ? • Impact – How much trouble does problem cause to users ? • Persistence – One-off problems that users “figure out” • Example: Patriot web login, must go to another screen – Repeated trouble • Persistent confusion • Note: Persistently abused users eventually just leave • Patriot web example: Faculty menu -> Summary Class List -> Select a Term -> Select a CRN -> Faculty menu -> Summary Class List … HUH? 1 July 2016 © Offutt 5 Hospital Order-Entry System • Dosage listed in “units of medication,” 20mg or 30mg – Pills stored in 10mg doses – Subtle message (default) : 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! Bad usability makes good systems bad ! 1 July 2016 © Offutt 6 The Scale of Misery—All Severities • IA = Information Architecture • Findability (IA, Category names, Navigation, Links) causes 26% of all problems • 37% of all problems caused by users not finding the right page 1 July 2016 © Offutt 7 The Scale of Misery (2) • Usability problems are weighted by severity score • Huge proportion of misery in basic functions : – Finding information – Reading information – Understanding information • Roughly 37% of difficulties are about getting to right page • Roughly 62% of difficulties are at the page level – Bad page or confusing sequence of pages If they can’t find it, they can’t buy it ! 1 July 2016 © Offutt 8 Why Users Fail 6 15 10 13 27 19 Search Findability Page Design Information Task support Fancy design Other 10 Navigation, navigation, navigation 1 July 2016 © Offutt 9 Is it Enough to Focus on the Worst Problems? • Multiple minor problems can drive users off • Many of the minor problems are trivial to fix Prioritization is a high level leadership responsibility 1 July 2016 © Offutt 10 Summary No matter how many problems you fix Quality must be designed in From the beginning 1 July 2016 © Offutt 11