The Law School Admission Test: Reliability and Validity in Brief
A holistic admission process that includes a reliable and valid standardized assessment as one factor best promotes diversity, equity, access, and excellence in admission and enrollment.
The reliability of a test is a measure of the precision of the scores reported on that test. To assess the reliability or consistency of LSAT scores, a reliability coefficient is computed for each LSAT test form. Reliability coefficients indicate how reproducible a test taker’s performance would be over repeated administrations of that test. Reliability coefficients are measured on a scale from 0 to 1. The larger the value of the reliability coefficient, the more reproducible a test taker’s performance should be. Values of at least 0.9 indicate a very reliable test form.
Reliability coefficients for LSAT test forms are published in LSAC’s annual Interpretive Guide for LSAT Score Users. LSAT test forms typically have reliability coefficients over 0.9. In the most recent testing year, the reliability coefficient values for LSAT forms have ranged from 0.92 to 0.94, indicating that the LSAT is a highly reliable test.
Demonstrating the validity of an admission test for an academic program requires strong evidence that justifies the use of that test to make admission decisions for the program (Kane, 2006). Test publishers need to demonstrate validity empirically, which is the focus of this summary. Two of the most important scientific standards for demonstrating validity empirically for a high-stakes admission test are construct and predictive validity.
Is the admission test measuring skills relevant to success in the program for which it is being used?
The LSAT is the only valid and reliable test designed for law school admission. Throughout its history, the LSAT has been built to assess the skills necessary for success in a law school curriculum. The LSAT is tailored to the law school curriculum, allowing schools to appropriately assess candidates based on their likelihood of success in law programs. It does not measure skills not relevant for law school success. Not a mere general skills test, the LSAT measures the reading and comprehension of complex texts with accuracy and insight, the organization and management of information and the ability to draw reasonable inferences from it, the ability to think critically, the analysis and evaluation of the reasoning and arguments of others, and the ability to compose a persuasive argument. To ensure that the content of the LSAT aligns with the law school curriculum, LSAC researchers regularly survey law school faculty on the key skills required of law students. The most recent research study, conducted in 2018 and published in 2019, confirms the LSAT assesses the skills most relevant for success in law school.
Does the test predict what it purports to predict?
The LSAT is designed to assist in the admission process by predicting success at the end of the first year of law school (1L). For many decades, LSAT scores consistently have been shown to be the single best predictor of 1L grade point average, even more highly predictive than undergraduate grade point average. In addition, the combination of undergraduate grade point average and LSAT score has consistently been shown to provide the best predictive model for 1L success.
LSAC-published reports document the predictive validity of the LSAT. Among those reports are the following:
- Evidence to Support Validity Claims for Using LSAT Scores in Law School Admission
- 2017-2019 LSAT Correlation Study Results (PDF, 605 KB)
- Predictive Validity of the LSAT: A National Summary of the 2013 and 2014 LSAT Correlation Studies (PDF, 473 KB)
Kane, M. T. (2006) Validation. In R. Brennan (Ed.), Educational Measurement, 4th Edition (pp. 17-64). Washington, DC: American Council on Education.