City tests and information theory.

The responses of 455 male subjects on both editions of the City University Colour Vision Tests (City 1 and City 2) were recorded after the establishment of each subject's criterial status using the Nagel anomaloscope. Based on the Information Theory, each plate was assigned a contributory weighted score to the total test score. Using informational analysis, a cut-off point in test score separating normals and defectives was also determined for each test. This scoring system is an improvement on the existing (or manufacturer's) system. The analysis has also shown that the second edition (City 2) is a considerable improvement on the first (City 1). Despite this, even the improved City 2, like its origin, the D-15, is shown to be poorer than most of the commonly used PIC tests.