Human Computer Interaction Flashcards
Why study usability
We want to support and enhance human activity, so we should design with the users in mind. Technology is not useful unless it is usable! Usable systems lead to increased productivity and greater satisfaction.
HCI
Human-computer interaction is a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of the major phenomena surrounding them.
Measurement of Usability
In order to measure the usability of an interface we can measure five attributes:
Learnability Memorability Efficiency of Use Error Subject Satisfaction
These attributes can be used to define measures of a system’s usability and to measure the success of a system interface.
Learnability
How fast can a user learn to use an interface sufficiently well to accomplish basic tasks?
“Easy to learn” refers to a novice user’s experience
Measurement of this attribute involves measuring the increased proficiency reached by users completing tasks after a specified period of training
Memorability
If a user has used the system at some earlier date, can he or she remember enough to use it effectively next time? The system (metaphor) should be easy to remember. Casual users can return to the system after some period of time without much relearning!
Measurement can be done on users after a period of no use, or a memory test can be conducted after a test session
Built-in methods of reducing the need to remember e.g. email addresses
Efficiency of use
Once an experienced user has learned to use the system, how fast can he or she accomplish tasks? High level of productivity is possible. Once a user reaches expert status, one can measure how much faster that user can complete a task, compared with the time they took before they were provided with the system
Errors
Error-related factors: How often do users make errors while using the system, how serious are these errors, and how easy is it to recover from a user error? An error is any action which inhibits the accomplishing of a desired goal. One can measure the error rate – the number of errors that occur while performing a specified task. Catastrophic errors should NEVER occur!
Subject Satisfaction
Systems should be pleasant to use. Entertainment value can be more important than the speed with which things get done. This is measured by asking users for their subjective opinions of the system after they have experienced its use
Heuristics
Heuristics are strategies using readily accessible, though loosely applicable, information to control problem solving.
Heuristics can be mental shortcuts that ease the cognitive load of making a decision. A rule of thumb or aneducated guess.
Interface design heuristics
Usability statements that guide a developer’s design efforts. Derived by evaluating common design problems across many systems
10 Interface Design Heuristics/Principles
LANGUAGE
CONSISTENCY
MEMORY
FEEDBACK
EXITS
SHORTCUTS
ERRORS
HELP
SCREEN DESIGN
Use Simple and Natural Dialogue
Use the user’s conceptual model. Match the users’ task in as natural a way as possible – minimise mapping
Be consistent
Consistency of effects
Same words, commands, cause the system to perform the same actions in similar situations (predictability)
Consistency of language and graphics
Same formation/controls in same location
Same visual appearance across system
Speak the users language
Use terminology based on the users’ language. Use meaningful mnemonics, icons, and abbreviations. Cater for multiple interaction styles (eg File/Save – Save Icon, Menu, Ctrl +S)
Minimise the users memory load
Promote recognition over recall.
Affordance
An aspect of an object which makes it obvious how the object is to be used.
Icons - symbolise computer actions
Menus - Menus provide a variety of prompts to help the user
