Derivation and Validation of the Automated Readability Index for Use with Technical Materials

The utility of technical materials is influenced to a marked extent by their reading level or readability. This article describes the derivation and validation of the Automated Readability Index (ARI) for use with technical materials. The method allows for the easy, automatic collection of data as narrative material is typed on a slightly modified electric typewriter. Data collected includes word length (a measure of word difficulty) and sentence length (a measure of sentence difficulty). Appropriate weightings of these factors in a multiple regression equation result in an index of reading difficulty. Uses of the index for evaluating and controlling the readability of large quantities of technical material are described.