Design Principles

Good design follows identifiable principles - whether it is the design of a door handle, a video cassette player, or a teapot. These principles apply no less to the design of interactive statistical analysis systems.

In his book, The Design of Everyday Things, D.A. Norman (1988) develops several principles of good (and bad) design which he illustrates using objects from every day life. These can be reduced to the following five principles of design:

M.

Match mental models

S.

Simplify structure

C.

Constrain

E.

Expect error

F.

Failure? Fix on a standard.

The principles are discussed in turn below and illustrated with the design choices of the interactive statistical system called Quail (see Oldford et al below to access the software, and Oldford, 1998, for some further detail on Quail). Figure shows the screen of a typical session in Quail.