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Usability. When 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

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Whenyou design the userinterface to a computer system, youdecidewhichscreens the system will show, whatexactlywillbe in each screen and how it will look. Youalsodecidewhat the usercanclickon and whathappenswhenhedoes so, plus all

the otherdetails of the userinterface.

It is the designer’sresponsibilitythat the system has adequateusability – it can do what is needed and is easy to use. It is the programmer’sresponsibilitythat the computer actuallybehaves as the designer prescribed.

Why usability is hard

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

Iterative design

  • Let developers study the users and theirtasks as part of analysis (taskanalysis)

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

  • Usability test the prototype with typicalusers. Correct the prototype to removeusability problems, test again and so on until the result is satisfactory. This is iterative design.


The Hospital system

Prototypes of user interface

Prototypes of user interface

  • Hand-drawnmock-up

  • Tool-drawnmock-up

  • Screen prototype (littlefuctionality)

  • Functional prototype (functionality with Buttens)

Prototyping for tiny fingers

Prototyping for tiny fingers

  • Prototyping on paper (lowfidelity – lo-fi). One person actslike an computer the othersobserve and take note notes. Allowsyou to demonstrate the behavior of an interface veryearly in development and test designs with real users.

  • Multimedia-tools (highFedelity-hi-fi) have beenused for manyyears, but it take to long time to createansiterationswillbe lost.

Building a lo fi prototype

Building a lo-fi prototype

  • Assamble a kit (get all the materialyouneed).

  • Set a deadline a short one so youcantake the most importantaspects of your design down on paper for testing

  • Construct models, not illustrations ( makesomethingthatwillbeeasy for the person playing computer).

  • Construct a first version completely by hand.

Preparing for test

Preparing for test

  • Select yourusers (with a gooduser profile on handyoucandevelop a questionnairethatwillhelp to chose the bestrepresentativeusers from availablecandidates). See figure 2 for lo-fitesting.

  • Prepare test scenarious

  • Practice (eachteammember must becomfortable with his or her role. In thiswayyouwill not have human bugs in the system)

Conducting a test

Conducting a test

  • It takes 4 people to get the most out of an test section.

  • Greeter – welcomesusers

  • Facilitator – giving the userintroduction. Encouraging the user to express his or her’sthoughtsduring the test and making sure thateverything is done in time.

  • Computer

  • Observers

    The test willtakeonehour. Afterwardsspend 10 min to debrief.


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