This paper introduces a class of graphical independence models that is closed under marginalization and conditioning but that contains all DAG independence models. This class of graphs, called maximal ancestral graphs, has two attractive features: there is at most one edge between each pair of vertices; every missing edge corresponds to an independence relation. These features lead to a simple parameterization of the corresponding set of distributions in the Gaussian case.

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Explaining how entrepreneurs overcome information asymmetry between themselves and potential investors to obtain financing is an important issue for entrepreneurship research. Our premise is that economic explanations for venture finance, which do not consider how social ties influence this process, are undersocialized and incomplete. However, we also argue that organization theoretic arguments, which draw on the concept of social obligation, are oversocialized. Drawing on the organizational theory literature, and in-depth fieldwork with 50 high-technology ventures, we examine the effects of direct and indirect ties between entrepreneurs and 202 seed-stage investors on venture finance decisions. We show that these ties influence the selection of ventures to fund through a process of information transfer. (Entrepreneurship; Venture Finance; Social Capital) Entrepreneurs are often wealth constrained, and need to obtain external financing to pursue their opportunities, making financing central to the process of entrepreneurship (Evans and Leighton 1989, Casson

A family of scaling corrections aimed to improve the chi-square approximation of goodness-of-fit test statistics in small samples, large models, and nonnormal data was proposed in Satorra and Bentler (1994). For structural equations models, Satorra-Bentler's (SB) scaling corrections are available in standard computer software. Often, however, the interest is not on the overall fit of a model, but on a test of the restrictions that a null model say M 0 implies on a less restricted one M 1 .IfT 0 and T 1 denote the goodness-of-fit test statistics associated to M 0 and M 1 , respectively, then typically the difference T d = T 0 ; T 1 is used as a chi-square test statistic with degrees of freedom equal to the difference on the number of independent parameters estimated under the models M 0 and M 1 . As in the case of the goodness-of-fit test, it is of interest to scale the statistic T d in order to improveitschi-square approximation in realistic, i.e., nonasymptotic and nonn...

This article examines the theoretical status of latent variables as used in modern test theory models. First, it is argued that a consistent interpretation of such models requires a realist ontology for latent variables. Second, the relation between latent variables and their indicators is discussed. It is maintained that this relation can be interpreted as a causal one but that in measurement models for interindividual differences the relation does not apply to the level of the individual person. To substantiate intraindividual causal conclusions, one must explicitly represent individual level processes in the measurement model. Several research strategies that may be useful in this respect are discussed, and a typology of constructs is proposed on the basis of this analysis. The need to link individual processes to latent variable models for interindividual differences is emphasized. Consider the following sentence: “Einstein would not have been able to come up with his e � mc 2 had he not possessed such an extraordinary intelligence. ” What does this sentence express? It relates observable behavior (Einstein’s writing e � mc 2)toan unobservable attribute (his extraordinary intelligence), and it does so by assigning to the unobservable attribute a causal role in

Employees' Organizational Identification (OI) is measured in a customer service organization. Particularly the effects of employee communication and perceived external prestige (PEP) on OI were evaluated. Results show that employee communication affects OI more strongly than PEP. One aspect of employee communication, the communication climate, appears to play a central role: it mediates the impact on OI of the content of employee communication. These results suggest that the importance of how an organization communicates internally is even more vital than the question what is being communicated. Consequences of the results for managing and synchronizing internal and external communication are discussed. Employees who identify strongly with their organization are more likely to show a supportive attitude toward it (Ashforth & Mael, 1989), and to make decisions that are consistent with organizational objectives (Simon, 1997: 284). Organizational identification may induce employees to...

The purpose of this study is to explore an Information System (IS) student retention model by modifying the integrated model of Tinto and Bean. The proposed model extends the integrated model by adding a construct named self-efficacy which is a psychological factor borrowed from self-efficacy theory. Data was collected from six private institutions in Taiwan and participants included students studying in the IS discipline in 2009. Structural equation modelling was utilised to validate the proposed model. Although the measures used in assessing the fit of the model obtained reflected the overall strength of the hypothesized model, the present study was not entirely supportive of Tinto’s or Bean’s models. Based on the significance of the factors in affecting the retention of IS students, the following intervention programs are suggested: (1) promoting self-efficacy programs, (2) provision of career consultancies and services, and (3) improvement of the teaching of IS core courses.

championship in Dieren, and to the Royal Dutch Chess Federation (KNSB) as personified by Patrick Razenberg. We thank Sandra de Blécourt and Jaap Kamminga for their help in constructing tests and collecting the data, Harry Vorst for constructing the motivation questionnaire, Conor Dolan for assisting in the LISREL analysis and Willemijn Roorda for assisting in the RT analysis. We also thank Karel van der Weide (International Master) and Dimitri Reinderman (International Grandmaster) for checking the test items and making valuable suggestions for improvement. We thank Neil Charness, Anders Ericsson, and Fernand Gobet for their valuable comments on a previous draft of this article. More detailed information about the Amsterdam Chess Test as well as the test results is

In the social sciences, evaluating the effectiveness of a program or intervention often leads researchers to draw causal inferences from observational research designs. Bias in estimated causal effects becomes an obvious problem in such settings. This article presents the Heckman Model as an approach sometimes applied to observational data for the purpose of estimating an unbiased causal effect and shows how the Heckman Model can be used to correct for the problem of selection bias. It discusses in detail the assumptions necessary before the approach can be used to make causal inferences. The Heckman Model makes assumptions about the relationship between two equations in an underlying behavioral model: a response schedule and a selection function. This article shows that the Heckman Model is particularly sensitive to the choice of variables included in the selection function. This is demonstrated empirically in the context of estimating the effect of commercial coaching programs on the SAT performance of high school students. Coaching effects for both sections of the SAT are estimated using data from the National Education Longitudinal Study of 1988. Small changes in the selection function are shown to have a big impact on estimated coaching effects under the Heckman Model.

After the evaluation of numerous technology integration programs in school districts and universities, it is recognized that the existence of technology does not guarantee its utilization in the classroom environment. Although many models and theories have tried to explain the contributing factors in technology acceptance, most of the models and theories have focused on technology-related factors. This study focused on educational ideology, a factor not related to technology that also affects decisions in terms of educational applications. Based on the literature review, we hypothesized a new model of technology acceptance which includes educational ideology as an external factor. We attempted to create a model that was compatible with our hypothesized model by collecting data from surveys completed by 320 pre-service teachers. Structural Equation Modeling was employed to create the path analytic model. The variables used in the path analytic model were the components of the original Technology Acceptance Model and six different educational ideologies. The results showed that the new model was consistent with the hypothesized model. Therefore, the results illustrate that different educational ideologies may have different effects on teachers’ technology acceptance.