Differential Item Functioning Assessment in Cognitive Diagnostic Modeling: Application of the Wald Test to Investigate DIF in the DINA Model

Analyzing examinees’ responses using cognitive diagnostic models (CDMs) has the advantage of providing diagnostic information. To ensure the validity of the results from these models, differential item functioning (DIF) in CDMs needs to be investigated. In this article, the Wald test is proposed to examine DIF in the context of CDMs. This study explored the effectiveness of the Wald test in detecting both uniform and nonuniform DIF in the DINA model through a simulation study. Results of this study suggest that for relatively discriminating items, the Wald test had Type I error rates close to the nominal level. Moreover, its viability was underscored by the medium to high power rates for most investigated DIF types when DIF size was large. Furthermore, the performance of the Wald test in detecting uniform DIF was compared to that of the traditional Mantel‐Haenszel (MH) and SIBTEST procedures. The results of the comparison study showed that the Wald test was comparable to or outperformed the MH and SIBTEST procedures. Finally, the strengths and limitations of the proposed method and suggestions for future studies are discussed.     

World of work on TV: Ethnic and sex representation in TV drama

On the pages which follow, authors Seggar and Wheeler explore the increasing use of minority group members in network television programming. They focus on a sample period in 1971 to show variances in dramatic portrayals of minority versus white American roles. Dr. Seggar received his Ph.D. from Kentucky in 1968 and has since taught at Brigham Young University where he is now associate professor of sociology. Ms. Wheeler received her MA in sociology at BYU in 1971. An earlier version of this paper was first presented at the 1972 convention of the Association for Education in Journalism.     

Teacher perceptions of an online tutoring program for elementary mathematics

This study explores elementary teacher perceptions related to the implementation of an online tutoring program. Teachers were surveyed regarding factors that affected use of the online tutoring program as a supplement to mathematics instruction. Results indicated that teachers overwhelmingly reported positive views of the training and support opportunities provided, as well as confidence in their level of knowledge and the ease of use of the program. Teachers also indicated strong support of the mathematical content and instructional value of the program. Each of these factors increases the likelihood that online tutoring programs such as the one implemented in this study will continue to be used among teachers as a supplement to mathematics instruction.     

Navigating information spaces: A case study of related article search in PubMed

The concept of an “information space” provides a powerful metaphor for guiding the design of interactive retrieval systems. We present a case study of related article search, a browsing tool designed to help users navigate the information space defined by results of the PubMed^® search engine. This feature leverages content-similarity links that tie MEDLINE^® citations together in a vast document network. We examine the effectiveness of related article search from two perspectives: a topological analysis of networks generated from information needs represented in the TREC 2005 genomics track and a query log analysis of real PubMed users. Together, data suggest that related article search is a useful feature and that browsing related articles has become an integral part of how users interact with PubMed.     

The role of index compression in score-at-a-time query evaluation

This paper explores the performance of top k document retrieval with score-at-a-time query evaluation on impact-ordered indexes in main memory. To better understand execution efficiency in the context of modern processor architectures, we examine the role of index compression on query evaluation latency. Experiments include compressing postings with variable byte encoding, Simple-8b, variants of the QMX compression scheme, as well as a condition that is less often considered—no compression. Across four web test collections, we find that the highest query evaluation speed is achieved by simply leaving the postings lists uncompressed, although the performance advantage over a state-of-the-art compression scheme is relatively small and the index is considerably larger. We explain this finding in terms of the design of modern processor architectures: Index segments with high impact scores are usually short and inherently benefit from cache locality. Index segments with lower impact scores may be quite long, but modern architectures have sufficient memory bandwidth (coupled with prefetching) to “keep up” with the processor. Our results highlight the importance of “architecture affinity” when designing high-performance search engines.