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In the a-stratified method, a popular and efficient item exposure control strategy proposed by H. Chang (H. Chang and Z. Ying, 1999; K. Hau and H. Chang, 2001) for computerized adaptive testing (CAT), the item pool and item selection process has usually been divided into four strata and the corresponding four stages. In a series of simulation studies, researchers examined the optimum number of strata by systematically varying the number of strata, pool size (200, 400, and 800 items), item characteristics (0., 0.5 correlation between difficulty and discrimination), and item selection method (largest information, matching estimated ability with difficulty). Results show that quite independent of the item pool size and the correlation between item discrimination and difficulty, ability estimation deteriorated while the number of over- and under-exposed items decreased with an increase in stratum number. There is a diminishing return in that dividing the pool into too many strata can also be problematic because when the stratum is too small, there are not any items of close difficulty for each particular examinee. The results are in general agreement with the speculation that too few and too many strata may not provide optimum efficiency and balanced item pool utilization. It is shown that the ideal and optimum number of strata to be used in each specific application depend on the item pool structure, test length, and other testing conditions. (Contains 8 figures, 24 tables, and 8 references.) (Author/SLD)

Using structural equation modeling (SEM), researchers examined whether there was a general dominating factor that governed students' implicit theories of intelligence, morality, personality, creativity, and social intelligence. The possible age-related changes of students' implicit theories were also studied. In all, 1,650 elementary and junior high school students (grades 5 to 10) in a large Chinese city participated in the study. A set of questions about the personal attributes being studied was developed, and SEM was used to compare various competitive first- and second-order factor models. Results show a general and dominating implicit theory affecting students' beliefs about the individual personal attributes. In addition, students' entity theories seemed to be stronger as they grew older. However, whether these trends result from natural cognitive maturity or socialization remains to be explored. (Contains 18 references.) (SLD)

Test security has often been a problem in computerized adaptive testing (CAT) because the traditional wisdom of item selection overly exposes high discrimination items. The a-stratified (STR) design advocated by H. Chang and his collaborators, which uses items of less discrimination in earlier stages of testing, has been shown to be very successful in balancing and hence maximizing the usage of all items in the pool. However, under specific conditions such as the early stages of utilizing completely new item pools, it is possible that the STR strategy is slightly less efficient than the most widely used maximum information (Max-I) approach. In this series of simulation studies with variable length CAT in which testing terminates at a targeted test information, researchers examined whether the use of more items in STR to attain accuracy similar to the Max-I approach in ability estimation would result in a greater exposure of all items. Simulations with self-generated items as well as an operational pool support the usefulness of the STR method in general. However, the results suggest that it is desirable to have fewer in number but less discriminating items at earlier stages of testing and have a larger number of highly discriminating items at later stages. The limitations of this study and implications for future studies are discussed. (Contains 6 tables, 8 figures, and 12 references.) (Author/SLD)