Influence measure for the L1 regression

Because outliers and leverage observations unduly affect the least squares regression, the identification of influential observations is considered an important and integrai part of the analysis. However, very few techniques have been developed for the residual analysis and diagnostics for the minimum sum of absolute errors, L₁ regression. Although the L₁ regression is more resistant to the outliers than the least squares regression, it appears that outliers (leverage) in the predictor variables may affect it. In this paper, our objective is to develop an influence measure for the L₁ regression based on the likelihood displacement function. We illustrate the proposed influence measure with examples.     

Deconstructing maternal sensitivity: Predictive relations to mother‐child attachment in home and laboratory settings

Despite the well‐documented importance of parental sensitivity for child development, there is a lack of consensus regarding how best to assess it. We investigated the factor structure of maternal caregiving behavior as assessed at 12 months by the Maternal Behavior Q‐Sort (Pederson & Moran) with 274 mother‐infant dyads. Subsequently, we examined associations between these empirically‐derived dimensions and child attachment, assessed in the home and laboratory (final N = 157). Three dimensions of maternal behavior were identified, corresponding fairly closely to Ainsworth's original scales. They were labeled Cooperation/Attunement, Positivity, and Accessibility/Availability. Only Cooperation/Attunement consistently predicted home‐based attachment at 15 months and 2 years, and at comparable strength to the overall sensitivity score, suggesting that this construct may be central to sensitivity. At 18 months, compared to their primarily secure counterparts, different types of laboratory‐assessed insecure attachment were associated with different patterns of maternal behavior. Mothers in avoidant relationships (n = 18) were low on Cooperation/Attunement and Accessibility/Availability, but fairly high on Positivity. Mothers of disorganized infants (n = 11) were Cooperative/Attuned but somewhat less Positive toward, and less Accessible/Available to, their infants. A multidimensional approach to parental behavior may facilitate the identification of parenting precursors of insecure parent‐child relationships.     

Asymptotic robustness of least median of squares for autoregressions with additive outliers

This paper considers the robustness properties in the time series context of the least median of squares (LMS) estimator. The influence function of the LMS estimator is derived under additive outlier contamination. This influence function is redescending and bounded for fixed values of the AR parameters. The gross-error sensitivity, however, is an unbounded function of the AR parameters. In order to asses the global robustness behavior of the LMS estimator, we consider several notions of breakdown. The breakdown points of the LMS estimator depend on the value of the underlying AR parameter. Generally, the breakdown point is below one half for high values of the AR parameter. The bias curves of the LMS estimator reveal, however, that the magnitude of outliers has to be considerable in order to cause breakdown.     

Institutional Shifts In Inter-Municipal Service Delivery

Comparative research on inter-municipal cooperation in eight European countries shows that there is a great variety of institutional arrangements for cooperation across the different countries. Also, these arrangements tend to change over time in terms of the scope of cooperation among partners, their composition and the degree of organizational integration. This article describes and analyzes the variety of and shifts in institutional arrangements for a specific class of inter-municipal cooperation arrangements: those that are set up to provide for the joint delivery of public services. It is argued that specific arrangements are typically the outcomes of interaction between national institutional contexts, environmental factors and local preferences.     

Non-governmental organisations and philanthropy in Latin America: An overview

This article provides an overview of the emerging non-profit or voluntary sector in Latin America. Specifically, the article addresses the differences and communalities these non-profit organisations have across the region. It concludes by emphasising the huge variety of roles and functions performed by non-profit organisations within and across countries, and their often ambigious position between the private and public realms.     

The impact of risk aversion and ambiguity aversion on annuity and saving choices

Journal of Risk and Uncertainty - We analyze the impact of risk aversion and ambiguity aversion on the competing demands for annuities and bequeathable savings using a lifecycle recursive utility...     

University Students’ Attitudes Toward Same-Sex Parenting and Gay and Lesbian Rights in Portugal

The purpose of this study was to explore university students’ attitudes toward same-sex parenting and toward gay and lesbian rights. A total of 292 participants, aged between 18 and 27 (M = 21) responded to a questionnaire measuring attitudes toward parenting by gay men and lesbians, gay and lesbian rights, and beliefs about the etiology of homosexuality. Results revealed that the majority of students were against gay and lesbian parenting, gay and lesbian equal rights, and believed that homosexuality has a social/environmental basis. It was found that sexual prejudice is highly prevalent in Portuguese university students, and implications of these findings are discussed.     

Mimetic contagion and speculative bubbles

Conclusion The present essay has focused on specularity as a type of intersubjectivitywithin self-referential systems. We have stressed the self-organizationaldimension of specular processes, which lead to the emergenceof collective objects around which the group structures itself. Rationalbubbles, sunspots, and conventions provided us with examples of thiskind of self-organization within self-referential groups. It seems thatwe have here a theoretical schema that can account for numeroussocial institutions. Such is the case with money, which the overlappinggenerations model shows to belong to the same problematic. We haveobserved that individual and collective representations play an essentialrole in the definition of specular dynamics. In fact, giving thecollectivity a means of interpreting and understanding the natural andsocial environment is a crucial function of these representations. Inspite of its great importance, this cognitive dimension of collectiverepresentations has hardly been explored in previous theorizing. Wehave given priority to a specific form of specularity, namely, mimetism,which is in our view at the very heart of financial processes. Far frombeing the aberration that traditional approaches deem it to be, imita-tion is one of the most important types of rationality in situations ofuncertain and in situations where the agents' outcomes are highlyinterdependent. Our central hypothesis amounts to considering thatthe emergence of speculative bubbles on various kinds of markets canbe explained in terms of mimetic dynamics. Should this hypothesis beconfirmed, it would be possible to account for a phenomenon that isoften observed, namely, the link between bubbles and a decrease inthe diversity of opinion on the market. In our approach, conventionsare taken to be the outcome of a mimetic process. Conventions are thesocial objects created by a unanimous mimetic polarization.     

Control charts for monitoring the median in non-negative asymmetric data

Statistical Methods & Applications - Control charts are commonly used for monitoring the mean of processes. However, there are practical applications in which asymmetric data are the standard....