Quality Measurement for Documentation: Different Tools for Different Needs
http://www.stc.org/ConfProceed/1993/PDFs/Pg484485.pdf

Hunter, Claudia M.
STC Proceedings
1993

Abstract:

The world of technical communication continues to search for a reliable information metric that is easy to apply and widely accepted. Although that goal eludes us for the moment, we can make a choice among competing metrics based on an understanding of their strengths and weaknesses, and appropriateness for different audiences. Two kinds of metrics, ordinal scale metrics and surface feature metrics, seem to meet many of our needs. The differences between them lie in their choice of measurements and the methods of applying the measurements.