A New Readability Formula for Primary-Grade Reading Materials

IN RECENT YEARS there has been considerable interest in, and use of, formulas for judging the reading difficulty of printed materials. Most of this interest has dated from the offering in 1943 of the original Flesch formula (4). This formula and the later studies of Dale and Chall (3) have been used extensively in the evaluation of industrial communications, books, magazines, and government publications. A recent summary of articles and books dealing with readability studies lists over ninety-six publications on this topic in 1943-50 (5). An examination of these formulas and studies reveals that the interest has been focused largely on the evaluation of materials written for adults. None of the three leading formulasthe Flesch (4), the Lorge (7), or the Dale-Chall (3)-is applicable to materials written for individuals reading on levels below Grade IV. Other formulas, such as the Lewerenz (6) or Wilkinson (9) are available for evaluating primary materials, but, in the author's opinion, these are lengthy and cumbersome. Because of the obvious values in having objective measures of reading difficulty, the author and his co-workers have attempted to devise a formula that would be useful with primary-grade reading materials. There are a number of elements which may be used to estimate reading difficulty. Among these are word length, sentence length, and per cent of personal words or personal sentences. In addition, the number of syllables, the number of affixes or of prepositional phrases, and the proportion of difficult words mentioned in various word lists have been used. Dale and Chall have reviewed the relation of these various elements to reading difficulty. They find that the best prediction of reading difficulty is obtained from the number of difficult words (those outside a list of 3,000 words known to 80 per cent of fourthgraders) and average sentence length. Two other elements of almost equal predictive value are the number of affixes and the number of words outside the Dale list of 769 words (2). This is a list of the words found both in the International Kindergarten Union list (1) and the first 1,000 words of Thorndike and Lorge's Teacher's Word Book (8). The author and his co-workers have