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15.1: Using GOMS in the redesign of a phone-based response system


Usability consultant Bill Killam and his colleagues worked with the US Internal Revenue Services (IRS) to evaluate and redesign the telephone response information system (TRIS). The goal of TRIS is to provide the general public with advice about filling out a tax return-and those of you who have to do this know only too well how complex it is. Although this case study is situated in the USA, such phone-based information systems are widespread across the world.

Typically, telephone answering systems can be frustrating to use. Have you been annoyed by the long menus of options such systems provide when you are trying to buy a train ticket or when making an appointment for a technician to fix your phone line? What happens is that you work your way through several different menu systems, selecting an option from the first list of, say, seven choices, only to find that now you must choose from another list of five alternatives. Then, having spent several minutes doing this, you discover that you made the wrong choice back in the first menu, so you have to start again. Does this sound familiar?

Other problems are that often there are too many options to remember, and none of them seems to be the right one for you. The usability specialists used the GOMS keystroke level model to predict how well a redesigned user interface compared with the original TRIS interface for supporting users’ tasks. In addition, they also did usability testing.

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