Usability Evaluation/LP Usability: how to judge it

Usability Evaluation/LP Summary of Last Week Usability - quality of allowing user to accomplish tasks easily and fluently Usability principles in the non-digital world

Usability Evaluation/LP Usability Principles Visibility

Usability Evaluation/LP Good Mapping BAD GOOD

Usability Evaluation/LP Good Mapping - not just cookers

Usability Evaluation/LP Feedback This is a nice little kitchen timer unless you want to set a time less than 15 minutes. To do so you must first turn the indicator to a time greater than 15 minutes and then turn it back to the time you actually want! There is no indication of this on the front of the timer. What ends up happening is that you set times less than 15 minutes without first turning the indicator past 15 minutes. Then the timer doesn't go off.

Usability Evaluation/LP Regard to conventions

Usability Evaluation/LP Affordance Pull here Push here

Usability Evaluation/LP Ergonomic ease of use

Usability Evaluation/LP All these principles can be applied in the design of interactive systems - PC programs, Web sites, mobile phones, household machines, games… However, we need a way of judging whether usability has been achieved or not.

Usability Evaluation/LP How Do We Judge Usability? Leave it up to the designer? Design guidelines (e.g. mapping, affordance and so on) Watch people using the artefact? Empirical evaluation Get in some “expert” opinion Expert evaluation -> heuristic evaluation

Usability Evaluation/LP Heuristic Evaluation “Expert” evaluation method based on general usability principles. Heuristics = general rules about common properties of usable interfaces, e.g. give feedback. Also any other specific guidelines that may be relevant.

Usability Evaluation/LP 1. Create something to evaluate 2. Develop a set of scenarios for evaluators to attempt, focussed on crucial or problematic issues 3. Ask evaluators to attempt the scenarios 4. Evaluators make comments, for each heuristic 5. Compile results, normally at meeting How to do it

Usability Evaluation/LP + Can be used on paper versions, early in cycle + Produces good results, particularly if several experts used + Confidential + Experts can suggest solutions - May need to employ one or more consultants - Experts aren’t real users Pros and cons?

Usability Evaluation/LP Nielsen’s Heuristics 1 Visibility of system status The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.

Usability Evaluation/LP Nielsen’s Heuristics 2 Match between system and the real world The system should speak the users' language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.

Usability Evaluation/LP Nielsen’s Heuristics 3 User control and freedom Users often choose system functions by mistake and will need a clearly marked "emergency exit" to leave the unwanted state without having to go through an extended dialogue. “Undo” is important here.

Usability Evaluation/LP Nielsen’s Heuristics 4 Consistency and standards Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.

Usability Evaluation/LP Nielsen’s Heuristics 5 Error prevention Even better than good error messages is a careful design which prevents a problem from occurring in the first place.

Usability Evaluation/LP Nielsen’s Heuristics 6 Recognition rather than recall Make objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.

Usability Evaluation/LP Nielsen’s Heuristics 6a Show the possibilities Make objects, actions, and options visible. Don’t hide them unless there’s a reason.

Usability Evaluation/LP Nielsen’s Heuristics 7 Flexibility and efficiency of use Accelerators -- unseen by the novice user -- may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.

Usability Evaluation/LP Nielsen’s Heuristics 8 Aesthetic and minimalist design Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.

Usability Evaluation/LP Nielsen’s Heuristics 9 Help users recognize, diagnose, and recover from errors Error messages should be expressed in plain language (no codes), precisely indicate the problem and constructively suggest a solution.

Usability Evaluation/LP Nielsen’s Heuristics 10 Help and documentation Even though it is a worthy aim to design the system so that it can be used without paper-based help, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out and not be too large.

Usability Evaluation/LP Summary Judging usability isn’t a question of personal preference: there are a variety of more dependable methods. Heuristic evaluation is a principle-based approach, carried out without user involvement. Tutorials - in labs. Practice of heuristic evaluation