Constructing Rotating Item Pools for Constrained Adaptive Testing

Preventing items in adaptive testing from being over- or underexposed is one of the main problems in computerized adaptive testing. Though the problem of overexposed items can be solved using a probabilistic item-exposure control method, such methods are unable to deal with the problem of underexposed items. Using a system of rotating item pools, on the other hand, is a method that potentially solves both problems. In this method, a master pool is divided into (possibly overlapping) smaller item pools, which are required to have similar distributions of content and statistical attributes. These pools are rotated among the testing sites to realize desirable exposure rates for the items. A test assembly model, motivated by Gulliksen's matched random subtests method, was explored to help solve the problem of dividing a master pool into a set of smaller pools. Different methods to solve the model are proposed. An item pool from the Law School Admission Test was used to evaluate the performances of computerized adaptive tests from systems of rotating item pools constructed using these methods.     

Transition towards a green economy in Europe: Innovation and knowledge integration in the renewable energy sector

This paper investigates the fragmentation of the EU innovation system in the field of renewable energy sources (RES) by estimating the intensity and direction of knowledge spillovers over the years 1985–2010. We modify the original double exponential knowledge diffusion model proposed by Caballero and Jaffe (1993) to provide information on the degree of integration of EU countries’ RES knowledge bases and to assess how citation patterns changed over time. We show that EU RES inventors have increasingly built “on the shoulders of the other EU giants”, intensifying their citations to other member countries and decreasing those to domestic inventors. Furthermore, the EU strengthened its position as source of RES knowledge for the US. Finally, we show that this pattern is peculiar to RES, with other traditional (i.e. fossil-based) energy technologies and other radically new technologies behaving differently. Our results provide suggestive, but convincing evidence that the reduction in fragmentation emerged as a result of the EU support for RES taking mainly the form of demand-pull policies.     

Integration of children with specific language impairments

Abstract

Current knowledge of the integration of children with specific language impairment (SLI) is examined. The paper begins by defining this group of children and the nature of their difficulties. The heterogeneous characteristics of SLI children are discussed. It then addresses the educational provisions made for SLI children and the opportunities for integration present in different models of provision. Research on the integration of SLI children is evaluated with particular emphasis on the difficulties encountered by this group of children. The paper concludes with some thoughts for future research.