usability evaluation/lp usability: how to judge it

Usability Evaluation/LP

Usability: how to judge it


Summary of Last Week

Usability - quality of allowing user to accomplish tasks easily and fluently

Usability principles in the non-digital world


Usability Principles

Visibility


Good Mapping

BAD

GOOD


Good Mapping - not just cookers


FeedbackThis 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.


Regard to conventions


Affordance

Pull here

Push here


Ergonomic ease of use

www.baddesigns.com


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.


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


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.


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


+ 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?


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.



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.


Nielsen’s Heuristics 3User 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.


Nielsen’s Heuristics 4Consistency and standards

Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.


Nielsen’s Heuristics 5Error prevention

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



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.


Nielsen’s Heuristics 6a

Show the possibilities

Make objects, actions, and options visible. Don’t hide them unless there’s a reason.



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.



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.



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.



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.


SummaryJudging 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

usability evaluation/lp usability: how to judge it

Documents

nielsens heuristics

system functions

visibility of system

systemoriented terms

general usability principles

freedom users

user control

users language