Usability is not an add-on Steven Pemberton CWI, Amsterdam

A thought experiment zWhat are the features of websites that you go back to regularly that differentiates them from other websites with the same purpose?

Differentiating features zForrester did some research in this yGood content (75%) yUsability (66%) ySpeed (58%) yFrequency of updating (54%) y(The rest is noise: 14% and lower)

This is surprising zUser testing is the first item to go when looking for reduced costs zMany web-building companies have no usability experts on their staff zMany web-building companies build sites that are measurably unusable

What is usability? zIt can be summarised by three factors: yEfficiency: how quickly you achieve what you want yEffectiveness: how correctly you achieve it ySatisfaction: how much you enjoy doing it

Compromises zSometimes these factors have to be balanced out: yAn experiment with 3 chess-playing interfaces (command-line, mouse, and real manipulation of chess pieces) showed that the mouse was the fastest yBut with real manipulation, the user won more often (was more effective)

Surprises zThe psychology of human beings can cause some surprising results: yIn a test with three methods of writing (pen on paper, a text editor, a word processor) users wrote less with a pen but of a higher quality, more with a text editor but of a lower quality, and more with a word processor but with a higher quality.

Transparency zA fourth aim of user interfaces is transparency: you don’t notice a good user interface, you spend all your time solving the problem.