UsabilityWhen you design the userinterface to a

computer system, you decide which screens the system will show, what exactly will be in each screen and how it will look. You also decide

what the user can click on and what happens when he does so, plus all

the other details of the userinterface.

It is the designer’sresponsibility that the system has adequate usability – it can do what is

needed and is easy to use. It is the programmer’s responsibility that the computer

actually behaves as the designer prescribed.

Why usability is hard

• It is a fact that system developers don’t know the users and their task as well as they know the computer. So the system will work fine on the computer but not with the users.

• Often the designers don’t design the userinterface until late in programming.

• Iterativ design is a way to improwe usability

Iterative design

• Let developers study the users and their tasks as part of analysis (task analysis)

• Make a prototype early in the design phase. Review it with expert users.

• Usability test the prototype with typical users. Correct the prototype to remove usability problems, test again and so on until the result is satisfactory. This is iterative design.

The Hospital system

Prototypes of user interface

• Hand-drawn mock-up• Tool-drawn mock-up• Screen prototype (little fuctionality)• Functional prototype (functionality with

Buttens)

Prototyping for tiny fingers

• Prototyping on paper (low fidelity – lo-fi). One person acts like an computer the others observe and take note notes. Allows you to demonstrate the behavior of an interface very early in development and test designs with real users.

• Multimedia-tools (high Fedelity-hi-fi) have been used for many years, but it take to long time to create ans iterations will be lost.

Building a lo-fi prototype

• Assamble a kit (get all the material you need).• Set a deadline a short one so you can take the

most important aspects of your design down on paper for testing

• Construct models, not illustrations ( make something that will be easy for the person playing computer).

• Construct a first version completely by hand.

Preparing for test

• Select your users (with a good user profile on hand you can develop a questionnaire that will help to chose the best representative users from available candidates). See figure 2 for lo-fi testing.

• Prepare test scenarious• Practice (each teammember must be

comfortable with his or her role. In this way you will not have human bugs in the system)

Conducting a test

• It takes 4 people to get the most out of an test section.1) Greeter – welcomes users2) Facilitator – giving the user introduction. Encouraging

the user to express his or her’s thoughts during the test and making sure that everything is done in time.

3) Computer4) ObserversThe test will take one hour. Afterwards spend 10 min to debrief.

Try it in the project