Provides step-by-step procedures for developing an index which uses the Gunning Fog technique to evaluate the level of reading difficulty of textbooks. Cites examples, illustrations, and several warnings in the discussion. (RT)

Reported is a study designed to determine whether reading grade level (RGL) assessment techniques used for elementary and secondary education textbooks would discriminate among plant and soil science textbooks. The study was to select the RGL indices suited to quantify the readability of these sources, and to identify the factors affecting…