Measuring Readability using DRP Units

The DRP is a new technique for measuring the readability of reading material. In this study, DRP-Difficulty scores were rescaled into grade equivalent (GE) units, called DRP-GE-Difficulty, and the reliability and validity of both versions were investigated. The formula for obtaining DRP-Difficulty is based on Bormuth's research that involved 330 passages sampled from curriculum materials. Using these same 330 passages, plus 30 more sampled from graduate school materials, the DRP-Difficulty scores were rescaled into DRP-GE-Difficulty units by finding comparable GE values obtained from the Rauding Scale of Prose Difficulty. The DRP-Difficulty and the DRP-GE-Difficulty scores correlated highly with cloze (-.84 and -.81, respectively), and with the grade level at which the passages were used (.80 and .78, respectively). DRP-GE-Difficulty values were found to be accurate to within about one grade level for materials used in the lower grades and to within about two grade levels in the upper grades. The DRP appears to provide estimates of readability that are reasonably reliable and valid.