Measuring Effect Sizes: The Effect of Measurement Error

Value-added models in education research allow researchers to explore how a wide variety of policies and measured school inputs affect the academic performance of students. The impacts of such interventions are typically quantified in terms of effect sizes. We estimate the overall extent of test measurement error and how this varies across students using the covariance structure of student test scores across grades in New York City from 1999 to 2007. Results reinforce the importance of accounting for measurement error, as it meaningfully increases effect size estimates associated with teacher attributes. There are important differences in teacher effectiveness that are systematically related to observed teacher attributes. Such effects are important in the formulation and implementation of personnel policies.