Measurement Properties of DIBELS Oral Reading Fluency in Grade 2

Abstract

Lack of psychometric equivalence of oral reading fluency (ORF) passages used within a grade for screening and progress monitoring has recently become an issue with calls for the use of equating methods to ensure equivalence. To investigate the nature of the nonequivalence and to guide the choice of equating method to correct for nonequivalence, the authors fit linear and nonlinear confirmatory factor analytic measurement models to Dynamic Indicators of Basic Early Literacy Skills (DIBELS) second-grade ORF passages routinely used for spring testing. They found evidence of nonlinear relations among passage scores that indicated equipercentile equating would be the best choice of equating method compared with mean or linear equating. The standard error of equating (SEE) with a sample of 600 participants was acceptable and less then two correct words per minute for equated scores from 0 to 150, which covers 95% and the useful range of scores. Consistent with the small SEE, the equating table also successfully removed all form differences in an independent sample of second graders. Given the widespread adoption of DIBELS in thousands of schools serving millions of students, equating all passages within a grade would substantially improve the quality of the tool and dramatically lower the assessment burden on school personnel.