Welcome to the memories page for IMPS 2009.
If you were able to attend this conference, we hope you found it both educational and enjoyable.
If you were not able to attend this conference, we hope to see you at future ones!
The program is available here.
We would like to extend our sincere congratulations all of our prize winners for 2009.
Best Dissertation: Bonne J.H. Zijlstra
Random effects models for directed graphs with covariates
A social network consists of a set of actors and the ties between them. The p2 model is a statistical model for the analysis of binary social network data with explanatory variables. It allows, for instance, to test whether a tie between two actors with a common property is more likely. The p2 model places special demands on the estimating algorithm because individual differences in sending ties (activity) and in receiving ties (popularity) are modeled using random effects. Because actors both send and receive ties, a cross-nested pattern of random effects results. For the p2 model newly developed Markov Chain Monte Carlo (MCMC) algorithms appear to provide estimates with small bias and adequate coverage rates. Utilizing the MCMC estimation, a multilevel p2 model, assuming multiple network observations to be representative of a population of social networks, is proposed. This may for instance be the case when networks in multiple school classes are observed. A multivariate p2 model, for the analysis of multiple networks observed on the same set of actors, is proposed as well. For friendship and advice networks between collegues, for instance.
Best Poster: Hibist Astatke
Testing the applicability of a theoretical model to predict ITN use in Ethiopia.
by Hibist Astatke, Mesfin Mulatu, Peter Buyungo, Daniel Crapper and Tsega Berhanu
About a third of Ethiopia’s population is at risk for malaria infection and young children represent the most vulnerable segment of the population. Use of insecticide-treated mosquito nets (ITN) is the primary mode of malaria prevention. Identifying theory-based psychosocial determinants of intention to use ITNs is important for designing effective malaria prevention programs. A survey was carried out with primary caregivers of children under five in systematically selected households (n = 1,206) in urban/semi-urban and rural areas in southern Ethiopia. Structural equation modeling (SEM) was applied to test the usefulness of Fishbein’s Integrative Model of health behavior linking psychosocial factors, social marketing communication, sociodemographic characteristics to intention to use ITNs. SEM results provided partial support for the model tested. As expected, positive attitudes and perceived social norms predicted intention to use ITNs. In contrast to expectation, perceived internal control and perceived availability were not significantly associated with intent to use. Overall, this theory-based model accounted for large proportion of variance in intention (43%). It is concluded that integrative health behavior models can be useful to explain ITN use and perhaps to developing interventions on ITN use in Ethiopia.
Best Junior Oral Presentation: Mariagiulia Matteucci
Including prior information in CAT administration.
by Mariagiulia Matteucci and Bernard P. Veldkamp
In this work, the use of empirical prior information in computerized adaptive testing (CAT) is investigated. Besides the individual responses, background variables concerning the examinees may be available and can be introduced in the estimation process. Whenever a strong relationship between the ability and the covariates is identified, it is possible to include collateral information both in the initialization and in the ability estimation process within CAT. Commonly, item selection in CAT is performed by adopting the maximum-information criterion. A serious consequence of applying this criterion is over exposure of the first item. Moreover, while research has been oriented towards using CAT to shorten the test length, adaptive testing shows a peculiar weakness especially when dealing with short tests. In the current work, a simulation study has been carried out in order to compare the accuracy of the ability estimates in case prior information is included or not. Special attention is given to the case of short tests. The findings show that, when empirical information is introduced, ability estimates are more precise, i.e. mean standard deviations are lower. Furthermore, the introduction of individual prior information reduces the item over-exposure, because the ability is initialized with reference to the examinee's covariates.
Our thanks to everyone who came to and participated in IMPS
We hope you had a great time, and hope to see you again in Athens, Georgia for IMPS 2010.
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