Usability 1 Usability evaluation Without users - analytical techniques With users - survey and observational techniques

Usability 2 Approach 1: Analytical evaluation cognitive walkthrough guideline-based analysis, in this case, heuristic analysis, but also standards inspection, consistency inspection

Usability 3 Cognitive Walkthrough

Usability 4 What is it? Evaluators look at the system from the user’s point of view They step through user tasks and predict where users will have problems They concentrate on learnability

Usability 5 How do you do it? (1) Preparation: Identify users We can use our personas Identify representative tasks We can use the scenarios Per task, describe the correct action sequence Obtainable from storyboard & site map Get a representation to work with Could be paper or rough/finished web pages Get evaluators

Usability 6 How do you do it? (2) Evaluators walk through the correct action sequence For each action, they indicate whether it is a “success story” or a “failure story” They provide evidence for their decision

Usability 7 Questions for each action Will the user: Expect to have to take this action? Notice the control for the action? Recognise that the control produces the desired effect? If the correct action is performed: Will progress be apparent?

Usability 8 Group walkthrough Performed by a mixed team Capture information on group displays (like flipcharts) Perhaps videotape whole process

Usability 9 Expect to have to do this? On a mobile phone, after entering a phone number, press the Send button.

Usability 10 Notice the control? Raising the window shade

Usability 11 Recognise the control? Turning the volume down

Usability 12 Will progress be apparent? Is the system doing something?

Usability 13 Cognitive Walkthrough of removing sound from an animation in PowerPoint Apples Pears Oranges Bananas

Usability 14 Analytical method 2: Heuristic Evaluation

Usability 15 Heuristic Evaluation What is it? “Expert” evaluation method based on general usability principles. Heuristics = general rules about common properties of usable interfaces.

Usability Create something to evaluate Can be paper prototype, active prototype, possibly a site map How to do it

Usability 17 Develop a set of tasks for evaluators to attempt, normally scenarios, focussed on crucial or problematic issues. Ask evaluators to go through the site several times and inspect the various navigation and information elements 2. Develop materials

Usability 18 Select at least 3-5 evaluators. The more evaluators, the more problems are discovered, but the benefit/cost ratio decreases at about 5 evaluators. Evaluators should not be associated with the project. Those with user interface or domain expertise find a greater percentage of actual problems (65%) and suggest a greater percentage of improvements than do developers (24%) or non-experts (12%). 3. Select Evaluators

Usability 19

Usability 20 Evaluators go through site with heuristics in mind, at least twice, once for pages, once for site design. May go through once for each heuristic - depends. Compile notes and write up report. Decide on relative importance and make a plan for tackling problems 4 Carry out evaluation

Usability 21 Which heuristics to use? Many lists exist Important that list is not too long Nielsen’s list of 10 heuristics Keith Instone (handouts) gives examples of how to use Nielsen’s heuristics for Web designs

Usability 22 Nielsen’s Heuristics Visibility of system status The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.

Usability 23 Match between system & real world

Usability 24 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.

Usability 25 Consistency and standards Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions, e.g. avoid custom link colours From Adobe Acrobat Reader

Usability 26 Error prevention Even better than good error messages is a careful design which prevents a problem from occurring in the first place.

Usability 27 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 28 Flexibility and efficiency of use Accelerators may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allowing bookmarks gives efficiency, as do other browser functions

Usability 29 Aesthetic and minimalist design A graphical counter-example: But on the Web, minimalist design also applies to text.

Usability 30 Help users recognise, 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 31 Help and documentation Even though it is better if the system can be used without documentation, 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.