Accuracy of Interpolation between Scale Graduations

Abstract

This study is concerned with the accuracy with which subjects can interpolate the position of a pointer or index between two scale graduations. Each of 20 subjects estimated the position of a mark on each of 99 5-in, linear, ungraduated scales. Estimates were given in units over the range 0–100 units. The median error was only 1.5% of the distance between the two marked graduations. Accuracy was greatest at the ends and middle of the scale. The data indicate that interpolation of fifths and even tenths will provide accuracy satisfactory for most situations.