Shortly after metric units of length were officially introduced in Australia in the 1970s, each of a group of 44 students was asked to guess, to the nearest metre, the width of the lecture hall in which they were sitting. Another group of 69 students in the same room was asked to guess the width in feet, to the nearest foot. The data were collected by Professor T. Lewis, and are given here in Table 3.1, which is taken from Hand et al. (1994). The main question is whether estimation in feet and in metres gives different results.