Differential Diagnosis

Differential Diagnosis
Minimal & In-depth Analysis
UCD Team Hyderabad

Nasarullah Khan f:09959406614 e: khan_nasar@hotmail.com

* what we’ll cover

 Why diagnosis/evaluation is important

 The three major types of diagnosis

 How to perform a heuristic evaluation


* why perform evaluations?

Risk reduction

 Evaluation and early redesign reduces the risk that final UI design will not meet
users’ needs

Cost and schedule savings

 Much less expensive to fix user interface problems during early project stages

 Can avoid schedule slippage due to user interface changes late in the project

Best time for initial evaluation: BEFORE coding begins


* major evaluation techniques

Inspection: experts examine an interface

 Example: heuristic evaluation

Empirical: users involved

 Example: usability testing (covered in evaluation class)

Formal methods: analytical techniques

 Example: Goals, Operators, Methods, Selection Rules


* heuristics evaluation origins
Developers of heuristic
Used to quickly determine an application’s compliance evaluation: Jakob Nielsen
with recognized usability principles known as
“heuristics”

Intended to be a cost-effective means of evaluating an
interface (“discount usability”)

 Increased speed of evaluation by using principles, not
guidelines (higher level of abstraction)

 Often can be performed when there is insufficient
time for any other type of evaluation


* heuristics evaluation: how to do it
Identify 3 - 5 evaluators (inspectors)
Tailor heuristics, and discuss tailoring so all evaluators understand heuristic usage
Each evaluator independently:
 Examines an interface and judges its compliance with heuristics
 Rates the severity of each problem found
After independent inspections, evaluators meet to:
 Discuss findings
 Eliminate duplicate problems
 Agree on ratings and summary findings


* severity ratings
Combination of:

 Frequency of occurrence

 Impact if it occurs

 One-time or persistent

Also need to assess the market impact

Nielsen recommends a 0 to 4 scale…

0: I don’t agree that this is a usability problem
1: Cosmetic only | 2: Minor | 3: Major | 4: Catastrophe


* nielsen’s heuristics (1994)
 Provide visibility into system status

 Provide a match between system and real world

 Allow both user control and freedom

 Follow standards to ensure consistency

 Prevent errors

 Allow for recognition rather than recall

 Provide flexibility and efficiency of use

 Use an aesthetic and minimalist design

 Help users recognize, diagnose and recover from errors

 Provide help and documentation


* description of heuristics
 Visibility of System Status – The system should always keep user informed about
what is going on, through appropriate feedback within reasonable time.

searching database for matches

 Match Between System and the Real World - The system should speak the user’s
language, with words, phrases and concepts familiar to the user, rather than system-
oriented terms. Follow real-world conventions, making information appear in a
natural and logical order.


 User Control and Freedom - Users should be free
to select and sequence tasks (when appropriate),
rather than having the system do this for them.
Users often choose system functions by mistake
and will need a clearly marked “emergency exit” to
leave the unwanted state without having to go
through an extended dialogue. Users should make
their own decisions (with clear information)
regarding the costs of exiting current work. The
system should support undo and redo.

 Consistency and Standards - Users should not
have to wonder whether different words,
situations, or actions mean the same thing. Follow
platform conventions.


 Error Prevention - Even better than good error messages is a careful design which
prevents a problem from occurring in the first place.

 Recognize Rather than Recall - Make objects, actions, and options visible. The user
should not have to remember information from one part of the dialogue to another.
Instructions for use of the system should be visible or easily retrievable whenever
appropriate


Edit
 Flexibility and Efficiency of Use - Accelerators-unseen by the Cut
novice user-may often speed up the interaction for the expert user
such that the system can cater to both inexperienced and Copy
experienced users. Allow users to tailor frequent actions. Provide Paste
alternative means of access and operation for users who differ from
the “average” user.

 Aesthetic and Minimalist Design - Dialogues should not contain information which
is irrelevant or rarely needed. Every extra unit of information in a dialogue competes
with the relevant units of information and diminishes their relative visibility.


 Help Users Recognize, Diagnose, and Recover from Errors - Error messages should
be expressed in plain language (NO CODES).

 Help and Documentation - Even though it is better if the system can be used without
documentation, it may be necessary to provide help and documentation. Any such
information should be easy to search, focused on the user’s task, list concrete steps to
be carried out, and not be too large.


* success is based on inspector skills
Three types of inspectors identified by Nielsen
 Domain expert
 Usability specialist
 “Double” expert

Double experts find most problems
 But you don’t have to be a UI expert to
use this technique!

Tends to find many problems of lesser severity
 Thus severity ratings are important


Thank You
Nasarullah Khan
Usability Engineer | User Experience Designer
f:09959406614 e: khan_nasar@hotmail.com


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