ERIC Number: ED469172
Record Type: Non-Journal
Publication Date: 1999-Aug
Reference Count: N/A
A Classical Test Theory Perspective on LSAT Local Item Dependence. LSAC Research Report Series. Statistical Report.
Reese, Lynda M.
This study extended prior Law School Admission Council (LSAC) research related to the item response theory (IRT) local item independence assumption into the realm of classical test theory. Initially, results from the Law School Admission Test (LSAT) and two other tests were investigated to determine the approximate state of local item independence (LID) found in actual test data. Yen's Q3 statistic was used for this purpose. Based on these analyses, four levels of LID were defined, and associated data sets generated. The average case was defined to represent the LSAT. Values of the r-biserial statistic and the alpha reliability index were studied to determine the effect of LID on these measures. Percentile ranks were also studied in order to assess the impact of LID for individual test takers. The results indicated that for extreme cases of LID, the discrimination power of individual items and the reliability of the total test are overestimated. Percentile ranks were also clearly affected by the introduction of a high level of LID, indicating that the impact for individual test takers should be of concern. Because the LID became problematic only at the most extreme level stipulated, the less than extreme level of LID typically displayed by the LSAT is probably not a problem with respect to these particular outcomes. (Contains 9 tables and 10 references.) (Author/SLD)
Publication Type: Numerical/Quantitative Data; Reports - Research
Education Level: N/A
Authoring Institution: Law School Admission Council, Newtown, PA.
Identifiers - Assessments and Surveys: Law School Admission Test