Optimal scaling of Metropolis algorithms: Heading toward general target distributions

The authors provide an overview of optimal scaling results for the Metropolis algorithm with Gaussian proposal distribution. They address in more depth the case of high‐dimensional target distributions formed of independent, but not identically distributed components. They attempt to give an intuitive explanation as to why the well‐known optimal acceptance rate of 0.234 is not always suitable. They show how to find the asymptotically optimal acceptance rate when needed, and they explain why it is sometimes necessary to turn to inhomogeneous proposal distributions. Their results are illustrated with a simple example.     

Improved model selection criteria for SETAR time series models

The purpose of this paper is threefold. First, we obtain the asymptotic properties of the modified model selection criteria proposed by Hurvich et al. (1990. Improved estimators of Kullback-Leibler information for autoregressive model selection in small samples. Biometrika 77, 709–719) for autoregressive models. Second, we provide some highlights on the better performance of this modified criteria. Third, we extend the modification introduced by these authors to model selection criteria commonly used in the class of self-exciting threshold autoregressive (SETAR) time series models. We show the improvements of the modified criteria in their finite sample performance. In particular, for small and medium sample size the frequency of selecting the true model improves for the consistent criteria and the root mean square error (RMSE) of prediction improves for the efficient criteria. These results are illustrated via simulation with SETAR models in which we assume that the threshold and the parameters are unknown.     

Some results on optimality in models with heteroscedastic errors from partial optimum designs

This paper studies optimum designs for linear models when the errors are heteroscedastic. Sufficient conditions are given in order to obtainD-, A- andE-optimum designs for a complete regression model from partial optimum designs for some sub-parameters. A result about optimality for a complete model from the optimality for the submodels is included. Supported by Junta de Andalucía, research group FQM244.     

The Ecology of Family Guidance in Low-Income Mexican-American and European-American Families*

This two-part study applied an ecocultural perspective to socialization of daily and long-term goals in low-income Mexican-American and European-American families with children in third, fifth, and seventh grades. The first part of the study examined family members' participation and parents' socialization goals and guidance strategies for their children's daily household chores and homework activities. The second part of the study examined parents' long-term aspirations and guidance strategies for their children's educational, vocational, and moral development. For daily activities, results showed that in Mexican-American families both parents and siblings played important roles, whereas in European-American families parents were the primary socialization agents. As predicted, in both groups parents' expertise influenced their guidance strategies. Finally, Mexican-American and European-American parents differed in their relative endorsement of gender, relational, and self-reliance goals for household chores. For long-term goals, parents in both groups held high educational, vocational, and moral aspirations for their children. However, some parents of seventh-graders had lower educational and vocational aspirations than those of fifth- and third-graders. Although expertise consistently influenced Mexican-American parents' guidance strategies, the pattern for European-American parents was mixed. The discussion highlights between- and within-group differences in daily and long-term socialization practices with an emphasis on resources and vulnerabilities in the families.     

How bad can a voting location be

Two questions concerning the location of a single facility by a voting process are investigated for transportation networks:

- What is the maximum number of customers located on the network preferring some rival point over a voting solution?

- How does the average distance of the customers to the facility increase when a voting location instead of a Weber location is chosen for the facility?

Complete answers are given for general networks and for certain planar networks, viz., the so-called generalized cacti.     

Leveraging middle managers’ brokerage for corporate entrepreneurship: The role of multilevel social capital configurations

Building on recent efforts to bring a socio-political perspective to social capital research, we develop and test a multilevel framework that explains why middle managers who occupy brokerage positions differ in their ability and willingness to engage in entrepreneurial behavior. More specifically, we provide a contextualized understanding of the links among middle managers' brokerage, their political-support ties, and their personal initiative. Results derived from data on 383 middle managers and 72 top managers in 34 business units indicate that political-support ties with top managers strengthen the relationship between middle managers’ brokerage and personal initiative. However, this positive effect depends on the social capital resources available in the focal business unit. It is attenuated in business units with a supportive and trusting social context and amplified in business units with high levels of internal connectedness. By uncovering these incompatibilities and complementarities, our study demonstrates the value of accounting for different social capital configurations and the interplay of their inherent social capital resources when examining the effects of brokerage on corporate entrepreneurship.     

The ecosystem blueprint: How firms shape the design of an ecosystem according to the surrounding conditions

Ecosystems are formed by organisations that jointly create a value proposition that a single firm could not create in isolation. To deliver this value proposition, the partners need a focal firm, the orchestrator, to be align them towards the joint value proposition. Thus, how orchestrators design the alignment structure of an ecosystem is at the very heart of the ecosystem concept – yet it has not been sufficiently addressed by extant research. This is all the more true for the question of how the design of an ecosystem is shaped depending on surrounding conditions. This paper applies a qualitative study with ten cases and, based on the attention-based view of the firm, contributes to research on ecosystems in several ways. First, it explains which ecosystem designs are beneficial under which conditions. Second, it elucidates the structure and activities within ecosystems and shows that start-ups can be just as good ecosystem orchestrators as incumbents. Third, it explains the circumstances under which single vs. multi orchestrator ecosystems occur. Fourth, it presents the conditions when incumbents or start-ups make better orchestrators. Finally, it is among the first studies to apply the attention-based view to business ecosystems, and shows that doing so yields intriguing insights into this emerging field of research.