Why do students’ Lexile measures reported by SRI sometimes differ from those reported by another assessment?
SRI produces a score, or estimate, of reading ability based on a well-defined set of procedures that make continual use of information collected while the student is taking the test. A Lexile reported by a paper-and-pencil test may differ from a Lexile reported by a computer-adaptive test simply because a paper-and-pencil test delivers the same items to each student, regardless of reading level, whereas a computer-adaptive assessment continually tries to deliver items that keep the student at a 75% comprehension rate, resulting in a more accurate Lexile measure. Two Lexiles derived from computer-adaptive assessments may also differ for several reasons. External factors aside, all tests have a Standard Error of Measurement (SEM) that will cause predictable variance in results. See the next question for details on the SEM of SRI.
