Everyday Design and Discount Usability Flashcards
Affordances
are those properties of the object which give users clues as to how the device is used
Discoverable affordance
can be easily found/discovered when interacting with the object and then interaction reveals other affordances
Hidden affordance
automatic appliance
puzzle boxes
easter eggs
Learnable affordance
feedback –> discovery
- glass breaks easily
- puzzle pieces
the more natural an affordance the easy it is to learn
Mapping
ensuring a correlation between objects and the interface controlling them
mapping associates
a potential action with a
particular reaction
Transfer effects
people transfer expectations from known objects to similar new ones
Previous experience conflicts with new situation :(
Previous experience applies to new situation :)
what can mappings and affordances depend on
Experience
knowedge
culture
relationships between affordances and constraints
constraints limit affordances
- helps user enter correct information
- restrict the field of possible actions
Costs making up the cost of quantitative testing
administrative - many users, user incentives, hiring and training
Usability expert person hours - study design and execution, stats analysis
special equipment
costs making up the cost of qualitative testing
admin - user compensation, travel and time
usability expert person hours - interviews, transcriptiom analysis
specialized equipment
benefits of discount usability techniques
cheap - no special labs or equipment
fast - fewer tester involved
easy to use - taught within 2-4 hours
Discount usability techniques examples
cog walkthroughs
heuristic eval
crowd sourcing
system usability scale
Describe a cognitive walkthrough
detailed task with concrete goal
action sequences for completion of task
will the users know what to do
will they notice that correct action is available
will the user interpret the feedback correctly
what would cause problems and why
Outcome of cog walkthrough
Each assessor prepares a list of issues -When did it occur? -What happened? -Severity Compile all reports into one -Note issues that occur frequently (more severe) -Prioritize the issues to be addressed
Pros of heuristic evaluation
catch design flaws
no users required
performed by experts
easy and inexpensive
cons of heuristic evaluation
more difficult than seems
will interface address user goals
not just a checklist
how to conduct heuristic evaluation
Small set (3-5) of evaluators (experts) examine UI:
check compliance with heuristics
different evaluators find different problems
evaluators can communicate afterwards to aggregate findings
designers use violations to redesign/fix problems
10 Usability Heuristics
visibility of system status match between system and real world user control and freedom error prevention aesthetic and minimalist design consistency and standards flexibility and efficiency of use recognition rather than recall help and documentation helo users recognize, diagnose and recover from errors
4 steps of heuristic evaluation
Pre-eval training
Evaluation
- two passes - get feel for flow and scope and then focus on specific elements
- produce list of problems (each evaluator)
Severity rating - rank issues
Debriefing
Why have multiple evaluations
one person will never be able to find all the problems in an interface
Severity rating scale meaning
0 - violates heuristic but not at all a usability issues
1 - cosmetic - only fix if there is time available
2 - minor usability issue- fixing should be given low priority
3 - Major usability issue: high priority
4 - usability catastrophe: imperative to fix this before release
Used to allocate resources
Estimates need for more usability efforts
Combine frequency, impact, and persistence
Should be calculated after all evaluations are in
Should be done independently by evaluators
What happens during debriefing
General discussion with evaluation participants
Brainstorm improvements to address major problems
Development team rates difficulty of fixing problems
Minimize criticism
pros and cons of heurisric evaluation
1-2 hours per evaluator
Findings are straightforward
May miss problems or find “false positives
pros and cons of user testing
Days or weeks of working with users
Requires interpretation of actions
Far more accurate: takes real users and tasks into account
key features of system usability scale
each item rated on 5 point likert scale
alternate between positive and negative questions
scoring - scale position vs reverse scale position
Interpret distributions not scores – convert list of scores to percentile distributions
Feels quantitative (because there’s numbers) but still subjective
when to use system usability scale
- SUS is not diagnostic. That is, it does not tell you what makes a system usable or not.
- SUS scores are not percentages, despite returning a value between 0 and 100
- people’s subjective assessments may not be consistent with whether or not they were successful using a system.
- Is SUS only for English speakers? Translations must be done with care and validated.
when and how to use quick and dirty techniques correctly and efficiently
- early design stages
- recognize its limitations
Not necessarily as comprehensive
80% or “good enough”
For a real usability evaluation, you may consider alternating or combining quick and dirty techniques with more comprehensive studies
