TY - JOUR AU - Clark,Melissa AU - Rothstein,Jesse AU - Schanzenbach,Diane Whitmore TI - Selection Bias in College Admissions Test Scores JF - National Bureau of Economic Research Working Paper Series VL - No. 14265 PY - 2008 Y2 - August 2008 UR - http://www.nber.org/papers/w14265 L1 - http://www.nber.org/papers/w14265.pdf N1 - Author contact info: Melissa A. Clark Mathematica Policy Research PO Box 2393 Princeton, NJ 08543-2393 E-Mail: mclark@mathematica-mpr.com Jesse Rothstein Goldman School of Public Policy University of California, Berkeley 2607 Hearst Avenue Berkeley, CA 94720-7320 Tel: 510/643-8561 Fax: 510/643-9657 E-Mail: rothstein@berkeley.edu Diane Whitmore Schanzenbach School of Education and Social Policy Northwestern University Annenberg Hall, Room 205 2120 Campus Drive Evanston, IL 60208 Tel: 847/491-3884 E-Mail: dws@northwestern.edu AB - Data from college admissions tests can provide a valuable measure of student achievement, but the non-representativeness of test-takers is an important concern. We examine selectivity bias in both state-level and school-level SAT and ACT averages. The degree of selectivity may differ importantly across and within schools, and across and within states. To identify within-state selectivity, we use a control function approach that conditions on scores from a representative test. Estimates indicate strong selectivity of test-takers in "ACT states," where most college-bound students take the ACT, and much less selectivity in SAT states. To identify within- and between-school selectivity, we take advantage of a policy reform in Illinois that made taking the ACT a graduation requirement. Estimates based on this policy change indicate substantial positive selection into test participation both across and within schools. Despite this, school-level averages of observed scores are extremely highly correlated with average latent scores, as across-school variation in sample selectivity is small relative to the underlying signal. As a result, in most contexts the use of observed school mean test scores in place of latent means understates the degree of between-school variation in achievement but is otherwise unlikely to lead to misleading conclusions. ER -