A method for determining invariant item parameters is presented, along with a scheme for obtaining test scores which are interpretable in terms of a common metric. The method assumes a unidimensional latent trait and uses a three parameter normal ogive model. The assumptions of the model are explored, and the methods for calculating the proposed…

When two different forms of a particular test are given to different groups of candidates, it is often necessary to make the test results for the two tests or groups as comparable as possible; the statistical process used for this purpose is termed equating. Two different methods of equating Graduate Record Examinations (GRE) Advanced Tests were…

Because it generally took over an hour to administer the Porch Index of Communicative Ability (PICA), a shorter but comparable version of the test was developed. The original test was designed to quantify aphasic patients' ability level on common communicative tasks and consisted of 18 ten-item subtests. Each item resulted in a proficiency rating,…

In Rasch terminology, two or more tests are linked when they are joined into a pool related to a single scale. When the same item calibrates at a low level on one test and a high level on a second test, it indicates that the item is low on the first test because the other items on that test are higher, and is high on the second test because the…

Five statistical indices are developed and described which may be used for determining (1) when linear equating of two approximately parallel tests is adequate, and (2) whan a more complex method such as equipercentile equating must be used. The indices were based on: (1) similarity of cumulative score distributions; (2) shape of the raw-score to…

Procedures are presented for equating simultaneously several tests which have been calibrated by the Rasch Model. Three multiple test equating designs are described. A Full Matrix Design equates each test to all others. A Chain Design links tests sequentially. A Vector Design equates one test to each of the other tests. For each design, the Rasch…

The problem of the comparability of change scores is investigated. Change quotients and residual change scores are evaluated as alternative approaches and methods for estimating the true change and true score residual, the reliability of change scores and residuals, and procedures for constructing confidence intervals for residuals are explored.…

This evaluation report is designed to meet two major objectives: a) to determine the extent of and the factors associated with variations in success and failure among children enrolled in the Distar Follow-Through programs, and b) to determine variations in success and failure in selected measures as they occur between children enrolled in the…

This research investigated the use of the Rasch simple logistic model in obtaining test-free ability estimates. Raw-score ability estimates were influenced by the difficulty of the items used in measurement but Rasch ability estimates were relatively independent of the item difficulty. (Author/CTM)

This study investigated whether differences in the dimensional structure of the form of the Law School Admission Test (LSAT) across selected ethnic subgroups of test takers had any impact on equating results using an item response theory (IRT) true-score procedure. Whether there were any differences in the underlying latent trait composite across…

With the advent of No Child Left Behind (NCLB), the context for NAEP participation is changing. Whereas in the past participation in NAEP has always been voluntary, participation is now mandatory for some grade and subjects among schools receiving Title I funds. While this will certainly raise school-level participation rates in the mandated…

This paper describes findings from two studies involving optional use of calculators on Scholastic Aptitude Test (SAT) mathematical items. The first study looked at the effects of calculator use on estimates of item difficulty. The second study looked at the effect of calculator use on equating results from an anchor test design. Study 1,…

It is now seen as an economic and political necessity for countries to produce higher levels of performance across the spectrum of ability of all their students. This paper describes one example of the influence of political conditions on the process of developing assessment instruments and on measuring standards. In England, the trend is toward…

This paper focuses on methodological issues in applying equipercentile equating methods to pairs of tests that do not meet the assumptions of equating. This situation is referred to as a concordance situation, as opposed to an equating situation, and the end result is a concordance table that gives "comparable" scores between the tests.…

Distinctions were made between three classes of statistical linkage: equivalence, concordance, and prediction. These distinctions were based on rational content considerations and empirical statistical relationships. A large database involving SAT I and ACT scores was used to determine which type of linkage was best suited for different scores and…