Discount Evaluation User Interface Design

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Marking It’s happening Highlights: People need to buy / sell Humans are not chattels Put your name on your assignment Do one thing well Infinite data storage is creepy TradeMe isn’t a single thing It’s hard to write good personas if you hate them or they are a joke Shop or auction What do you sell? Plain text is hard to format nicely Who likes using badly made things? Why would anyone use your system? Most of you assume that they will Scenarios should be small

Evaluation Different techniques for evaluating designs: Your best guess is not enough Testing with real users is expensive Nielsen’s Discount Usability Engineering: A cheap alternative “Le mieux est l’ennemi du bien” – Volatiare, 1764 (the best is the enemy of the good) Users aren’t designers Designers aren’t users

Discount Usability Techniques We are interested in techniques for this class: Heuristic Evaluation Cognitive Walkthrough These techniques have important weaknesses

How Many People Is Enough? Nielson says 3-4 people will find the majority of problems “The magic number 5” Nielson and Landauer, 1993 Law of diminishing returns? Is this true for all domains? Is it true for any domains?

Heuristic Evaluation 3 – 5 evaluators (everyone in the team) Guided by heuristics First pass by use case / scenario Second pass by context Rank problems 0 (not a problem) - 1 (cosmetic) – 4 (critical) Rank individually, then as a group

Nielsen’s 10 Heuristics - 1 Match between system and real word Speak the user’s language Not using system-oriented terms Follow existing conventions and ordering Visibility of system status The user is always aware of what is going on Feedback is timely User control and freedom Must support user errors Undo, redo, ‘emergency exit’

Nielsen’s 10 Heuristics - 2 Consistency and standards Words always mean the same thing Fonts, colours, sizes are the same for same type of things Follow platform conventions Error prevention Don’t put users in a situation where they are likely to make an error Make it more work to do something dangerous (like a conformation box) Recognition rather than recall Make actions, options and data visible Instructions should always be available Reuse things

Nielsen’s 10 Heuristics - 3 Flexibility and efficiency of use Accelerators should be there but invisible to the novice Should be able to customise the accelerator Aesthetic and minimalist design We’ll look at this in another lecture Help users recognise, diagnose, and recover from errors Plain precise English, and if possible suggest a solution Help and documentation Short and concrete (e.g. list of steps / tasks) Focused on tasks

Cognitive Walkthrough Experts go through the steps that users need to do to complete each goal For each step they ask: Will the user try to achieve the right effect? Will the user notice the correct action is available? Will the user associate the correct action with the effect to be achieved? After the action, does the user know that they are on the right path?

Cognitive Walkthrough Note that you do cheat a little bit to help structure the evaluation Evaluators start of knowing the correct route so they are checking against a model of expected behaviour It is not done by real users