§6.2 -- Principles of good design Flashcards
Which questions do we need to ask to distinguish good design from bad design?
- ease of determining function of the interface
- ease of determining possible actions
- how easily can users map intent to physical movements that need to be performed
- ease of performing the allowed actions themselves
- ability to infer the state of the system
Relevance of usability to good design
- Usability = how well users can learn/use product to achieve their goals + how satisfied they are with that process
sources of dissatisfaction: - Engineering usability - wrong physical design/technology/unreliable
- human user aspects – does not look good, frustrating
List of issues related to good design
- visibility
- feedback
- constraints
- consistency
- affordances
Visibility+example
- should be easy to determine possible actions and the functionality provided by the interface
e. g. lift buttons where need to scan card but hard to see card slot
consequences for inferring state of system (I press the button but nothing happens – am I doing something wrong or is the lift broken?)
Ways of making an action more visible
- make actions more obvious
- auditory messages (language?)
- big labels/lights
- make what has to be done obvious.
- avoid invisible automated controls (~ ease of performing the allowed actions themselves – wearing black if a tap control sensor does not respond to black clothing)
Feedback
– interface should send info back to user about what has been done (~ inferring state of the system, whether my action was successful or not)
via
- sound, highlighting, animation on button clicks
Constraints
restrict the possible actions that can be performed
~ ease of determining possible actions
~ decision burden/working memory/hicks law/fewer choices -> less decision time
- helps prevent user from selecting incorrect options
- physical design can impose constraints (E.g. only one way you can insert a key into a lock)
- avoid logically ambiguous designs (plugging mouse, ambiguous colour coded icons -> make more explicit e.g. place right next to connectors)
Consistency of an interface+why
interfaces should be designed to have similar operations for similar tasks
~~ 3. how easily can users map intent to physical movements that need to be performed
~ reduce probability of errors
e.g, keystroke begins with first letter of name of operation
~~ consistent interfaces are easier to learn + may be quicker to use if less need for recall / working memory /
Problems with maintaining consistency
- too many commands – e.g. keystrokes beginning with first letter
- have to choose other combinations of keys, breaking consistency rule
- increased learning burden on user => more prone to errors
Internal vs external consistency
IC – similar operations perform similar tasks within an application (test of system vs actual use – shouldn’t appear the same)
~~ difficult for complex interfaces (Hawaii)
EC – designing operations, interaces to be same across applications, devices (e.g. both mac and windows require double clicking on a folder to open it rather than just select it).
external inconsistency – different layout of keyboards on phones
Affordances
~ is an attribute of an object that allows people to know how to use it
~ e.g. mouse button invites pushing, door handle invites pulling
~ scrollbars to afford moving up/down,
~ icons to afford clicking
~ interfaces provide virtual affordances/perceived affordances
~ provides a mapping between action and the physical movements needed to perform the action
~ (ease of determining possible actions + mapping intent to physical movements)
List of Shneiderman’s 8 golden rules
- consistency
- universal usability
- informative feedback
- dialogs with closure
- preventing errors
- reversibility of actions
- user in control
- reduction of short term memory load
List of issues related to Golden Rule 1: Consistency
(terms, icons, data / command flow)
Strive for consistency in the way the system looks and works in terms of:
- terminology – e.g. identical words/terms for prompts, menus and help screens
- aesthetics – consistent colour codes, layout/font across different windows
- symbols – consistent use of icons, graphics
- response to inputs – system must respond to inputs in the same way every time
why does this help each of the key questions regarding good interfaces?
Golden Rule 2: Universal Usability
(novices → intermittent users → experts)
Allow frequent users to develop a clear idea of how the system works, and let them work faster
e.g.
- provide toolbars, keyboard shortcuts
- put the shortcut next to the menu entry for the command
.: novice uses menus
but menu allows them to easily learn the shortcuts
Golden Rule 3: Informative Feedback
every user action should result in some feedback from the system
- less prominent feedback for very frequently performed actions (e.g. button clicks)
- major actions require lots of response (e.g. installation of a new program – dialog box)
