Form effects on the estimation of students' oral reading fluency using DIBELS

This study examined the effects of passage and presentation order on progress monitoring assessments of oral reading fluency in 134 second grade students. The students were randomly assigned to read six one-minute passages in one of six fixed orders over a seven week period. The passages had been developed to be comparable based on readability formulas. Estimates of oral reading fluency varied across the six stories (67.9 to 93.9), but not as a function of presentation order. These passage effects altered the shape of growth trajectories and affected estimates of linear growth rates, but were shown to be removed when forms were equated. Explicit equating is essential to the development of equivalent forms, which can vary in difficulty despite high correlations across forms and apparent equivalence through readability indices.