R = .886593 - .083640 (LET/W) + .161911 (DLL/W)3 - 0.021401 (W/SEN) + .000577 (W/SEN)2- .000005 (W/SEN)3
DRP = (1 - R ) x 100
Where:
R = mean cloze score
LET = letters in passage X
W = words in passage X
DLL = Number of words in the original Dale-Chall list in passage X
SEN = Sentences in passage X
DRP = Degrees of Reading Power, on a 0-100 scale with 30 (very easy) to 100 (very hard)
The findings of Bormuth about the reliability of the classic variables were confirmed by MacGinitie and Tretiak (1971) who said that the newer syntactic variables proposed by the cognitive theorists correlated so highly with sentence length that they added little accuracy to the measurement. They concluded that average sentence length is the best predictor of syntactic difficulty.
The Bormuth studies provided formula developers with a host of new criterion passages. Critics of the formulas claimed that the criterion passages used by formula developers were arbitrary or out-of-date (Bruce et al. 1981, Duffy, 1985). As new criterion passages became available, developers used them to create new formulas and to correct and reformulate the older ones (Bormuth 1966, 1969, Klare 1985). The new Dale-Chall formula (1995) was validated against a variety of criterion passages, including 32 developed by Bormuth (1971), 36 by Miller and Coleman (1967), 12 by Caylor et al. (1973) and 80 by MacGinitie and Tretiak (1971). Other formulas were validated against normed passages from military technical manuals (Caylor et al. 1973, Kincaid et al. 1975).
The Fry Readability Graph While Edward Fry (1963, 1968) was working as a Fullbright scholar in Uganda trying to help teachers teach English as a second language, he created one of the most popular readability tests that use a graph.
Fry would go on to become the director of the Reading Center of Rutgers University and an authority on how people learn to read.
Fry's original graph determines readability through high school. It was validated with comprehension scores of primary and secondary school materials and by correlations with other formulas.
Fry (1969) later extended the graph to primary levels. In 1977, he extended it through the college years (Fig. 11). Although vocabulary continues to increase during college years, reading ability varies much, depending on both individuals and the subjects taught. That means that a text with a score of 16 will be more difficult than one with a score of 14. It does not mean, however, that one is appropriate for all seniors and the other for all sophomores.