Universal usability engineering

1. z
Usability
engineering
Neeraj Mohan 18352035

2. z
Software Quality (ISO
 Metrics and Evaluation
 Functionality
 Reliability
 Usability
 Efficiency
 Maintainability
 Portability
 PM Accessibility (sometimes relevant, not ISO 9126)

3. z
Definition of Usability (Nielsen
 Usability: how well users can use the system’s functio
 Usability is a quality attribute that assesses how easy
interfaces are to use
 The word ‘usability’ also refers to methods for improvi
use during the design process

4. z
Usability Comp Learnability
 Ease of learning the system, i.e. the basic tasks
 Skills retained over time (also Memorability)
 Throughput (also Efficiency)
 Speed of task performance
 Low user error rate
 Flexibility
 Suitability for intended user expertise
 Can system be customised?
 Attitude (also Satisfaction)
 User subjective satisfaction with system

5. z
Usability Components (Dimens
us
 Learnability: is it easy to learn?
 Memorability: is it easy to remember what you learne
 Efficiency: once learned, is it fast to use?
 Errors: are errors few and recoverable?
 Satisfaction: is it enjoyable to use?

6. z
The 5E’s to U
 Efficient
 The speed in which users complete their
 Error tolerant
 The ability of the interface to prevent erro
help users recover from those that occur
 Effective
 The completeness and accuracy with wh
achieve their goals
 Engaging
 How pleasant or satisfying the interface is

7. z
Usability Engin
 The test of usability based on
measurement of user experience
 It demands that specific usability
measures be made explicit as
requirements
 Usability Measurements
 Usability attribute/principle
 Measuring concept
 Measuring method
 Now level/ worst case/ planned level/ best case

8. z
Some metrics from ISOUsability Effectiveness Efficiency Satisfaction
objective measures measures measures
Suitability Percentage of Time to Rating scale
for the task goals achieved complete a task for satisfaction
Appropriate for Number of power Relative efficiency Rating scale for
trained users features used compared with satisfaction with
an expert user power features
Learnability % of functions Time to learn Rating scale for
learned criterion ease of learning
Error tolerance % of errors Time spent on Rating scale for
corrected successfully correcting errors error handling

9. z
Usability Engineering (
 Problems
 usability specification requires level of detail that may n
 possible early in design satisfying a usability specificat
 does not necessarily satisfy usability

10. z
Case Study-ATM (fro
 Researchers + banks expected ATMs to be intuitively
use
 Testing among senior citizens found only 20% correct
 Senior citizens often put off by ATMs they find the ma
 Complicated
 Inconvenient

11. z
Problems with
 Buttons that did not line up
with commands
 Screens hard to read in the
glare of daylight
 Sometimes confusing menu
choices

12. z
Usability sugge
 Simpler on-screen instructions
 More “undo” buttons
 Bank should provide training for any customers who n
 Remark:
 “Large percentage” of people surveyed said they would
trained

13. z
Key concepts Usability
 Cognetics- locus of attention
 Affordance
 What sort of operations and manipulation
done to an object
 Crucial is the perceived affordance
 Visibility
 Mapping between controls and effects sh
sensible and meaningful
 feedback

14. z
Important principle o
(Usa
 useful
 Accomplish what is required (functional, does things)
 usable
 Do it easily and naturally without error (does the right th
 used
 Make people want to use it (be attractive, acceptable to
organization)