Using Interval Likelihood Ratios in Gated Screening: A Direct Replication Study

Abstract

This direct replication study compared the use of dichotomized likelihood ratios and interval likelihood ratios, derived using a prior sample of students, for predicting math risk in middle school. Data from the prior year state test and the Measures of Academic Progress were analyzed to evaluate differences in the efficiency and diagnostic accuracy of gated screening decisions. Post-test probabilities were interpreted using a threshold decision-making model to classify student risk during screening. Using interval likelihood ratios led to fewer students requiring additional testing after the first gate. But, when interval likelihood ratios were used, three tests were required to classify 6th- and 7th-grade students as at-risk or not at-risk. Only two tests were needed to classify students as at-risk or not at-risk when dichotomized likelihood ratios were used. Acceptable sensitivity and specificity estimates were obtained, regardless of the type of likelihood ratios used to estimate post-test probabilities. When predicting academic risk, interval likelihood ratios may be best reserved for situations where at least three successive tests are available to be used in a gated screening model.