comu346 lecture 6 - evaluation
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TRANSCRIPT
Expert Evaluations & Design / Usability Heuristics
Will look at:• Need for alternatives to user evaluation• Methods of evaluating without end users
(using expert evaluators)• Some heuristics / guidelines offered by
experts
End User Evaluations
• End-user evaluations can be expensive– The methods are very time consuming– Users may not be willing– To get truly ‘fresh’ eyes, so called “kleenex”
testing requires different players each time
• Concerns about leaks– Few external play testers at early stages– Friends & family play testers may be too kind
Expert Evaluations
• As an alternative to some user testing, expert evaluators / testers can be used
• Falconer details 10 inspection methods, we will look at two:– Cognitive Walkthrough– Heuristic Evaluation
Cognitive Walkthrough
• In this approach experts imitate users– Relatively quick and cheap– Expert needs to be skilled and requires:
• A description of users (e.g. level of experience)• A description of system (or an operational system)• A description of the task to be carried out• A list of the actions required to complete the task
Cognitive Walkthrough
• Expert addresses questions such as:– Is the goal clear at this stage?– Is the appropriate action obvious?– Is it clear that the appropriate action leads to
the goal?– What problems (or potential problems) are
there in performing the action?
• Essential that the expert tries to think like the end user and not like themselves.
Consider Solium Infernum
• A scenario:– Goal is to go to war and capture building – Is the appropriate action obvious?
• What if no vendetta in place?– Is it clear that the appropriate action leads to the
goal?• Does the game help you?
– What problems (or potential problems) are there in performing the action?
• If you haven’t got vendetta status, how do you know?
• I know how to do this but thinking as a ‘user’ it’s not so easy.
Heuristic Evaluation
• Involves assessing how closely an interface or system conforms to a predefined set of guidelines or heuristics.
• Examples:– Nielsen’s usability heuristics– Schneiderman’s eight golden rules– Norman’s seven principles
Nielsen’s Usability Heuristics
• Give feedback – keep users informed about what is happening
• Speak the user’s language – dialogs should be expressed clearly using terms
familiar to the user
• User control and freedom– clearly marked exits and undo/redo
• Consistency and standards • Prevent errors
– even better than having good error messages
Nielsen’s Usability Heuristics
• Minimise memory load– recognition rather than recall
• Shortcuts– accelerators (unseen by novices) speed up
interactions for experts • Aesthetic and minimalist design
– don’t have irrelevant or rarely needed information • Good error messages
– should indicate the problem and explain how to recover
• Help and documentation– should be concise and easy to search
Norman’s 7 Principles
1: Use both knowledge in the world and knowledge in the head.
2: Simplify the structure of tasks.3: Make things visible.4: Get the mappings right.5: Exploit the power of constraints.6: Design for error.7: When all else fails, standardise.
Schneiderman’s heuristics (8 Golden Rules)
1. Strive for consistency 2. Enable frequent users to use shortcuts 3. Offer informative feedback 4. Design dialogues to yield closure 5. Offer error prevention & simple error handling 6. Permit easy reversal of actions 7. Support internal locus of control 8. Reduce short-term memory load
(Faulkner Chapter 7)
How Many Evaluators?
Different people find different problems.
http://bit.ly/heuristichowto
How Many Evaluators?