The advantages of administering an adaptive test battery, a collection of multiple adaptive subtests that are specifically tailored to examinees’ abilities, include shortening the subtest length and maintaining the accuracy of individual subtest scores. The test battery can incorporate a range of subjects, though this study focused primarily on Math and Reading. This study compared different ways of incorporating collateral information (CI), supplementary information beyond examinees’ current test performance, under two frameworks (Unidimensional and Multidimensional computerized adaptive testing). It also investigated the impact of subtest intercorrelations (the relationship between an examinee’s test scores), as well as the sequences of subtest administration on ability estimation in a variable-length adaptive battery. Practical issues including content constraints and item exposure control were also considered. Findings showed that the CI methods improved measurement efficiency with an acceptable level of measurement precision. The CI was more beneficial when associated with higher intercorrelations among the subtests. Also, the CI was found to be advantageous during the early stages of the subtests which were not taken first. Therefore, the CI may improve the examinee experience by administering items more aligned with their abilities. In addition, the CI should reduce costs for testing organizations by requiring fewer items and possibly saving seat time, while still providing reliable scores. The results should help practitioners decide whether the use of the CI is worthwhile under their particular testing situation.

Educators and administrators often use sub-scores derived from state accountability assessments to diagnose learning/instruction and inform curriculum planning. However, there are several psychometric limitations of observed sub-scores, two of which were the focus of the present study: (1) limited reliabilities due to short lengths, and (2) little distinct information in sub-scores for most existing assessments. The present study was conducted to evaluate the extent to which these limitations might be overcome by incorporating collateral information into sub-score estimation. The three sources of collateral information under investigation included (1) information from other sub-scores, (2) schools that students attended, and (3) school-level scores on the same test taken by previous cohorts of students in that school. Kelley's and Shin's methods were implemented in a fully Bayesian framework and were adapted to incorporate differing levels of collateral information. Results were evaluated in light of three comparison criteria, i.e., signal noise ratio, standard error of estimate, and sub-score separation index. The data came from state accountability assessments. Consistent with the literature, using information from other sub-scores produced sub-scores with enhanced precision but reduced profile variability. This finding suggests that using collateral information internal to the test has the capability of enhancing sub-score reliability, but at the expense of losing the distinctness of each individual sub-score. Using information indicating the schools that students attended led to a small gain in sub-score precision without losing sub-score distinctness. Furthermore, using such information was found to have the potential to improve sub-score validity by addressing Simpson's paradox when sub-score correlations were not invariant across schools. Using previous-year school-level sub-score information was found to have the potential to enhance both precision and distinctness for school-level sub-scores, although not for student-level sub-scores. School-level sub-scores were found to exhibit satisfactory psychometric properties and thus have value in evaluating school curricular effectiveness. Issues concerning validity, interpretability, suitability of using such collateral information are discussed in the context of state accountability assessments.