The two-sided power distribution for the treatment of the uncertainty in PERT

The aim of this paper is to include the Two-Sided Power (TSP) distribution in the PERT methodology making use of the advantages that this four-parameter distribution offers. In order to be completely determined, a distribution of this type needs, the same as the beta distribution, a new datum apart from the three usual values a (pessimistic), m (most likely) and b (optimistic). To solve this question, when using the beta distribution in the PERT context, we are looking for the maximum similarity with the normal and so it is required that the distribution has the same variance as the normal or its same kurtosis, giving rise to the constant variance and mesokurtic families, respectively. Nevertheless, while this approach can be only applied to the beta distribution for some values in the range of the standardized mode, in the case of the TSP distribution this methodology leads always to a solution. A detailed analysis comparing the beta and TSP distribution based on their PERT means and variances is presented indicating better results for the second. We are very grateful for the comments and suggestions of two anonymous referees.     

Employee and Volunteer

The purpose of this research is to analyze the different factors that determine the level of time devoted to volunteer activity involving employed people. To this end, we applied a logistic regression model to a sample of 5,067 employees, considering four categories of factors: family and personal, on the one hand, and contextual factors, on the other. This second group involves three factor categories: occupational, organizational, and community involvement factors. The findings of this work are especially relevant to two areas: first, to design a policy of corporate social responsibility that effectively integrates the figure of corporate volunteering, considering its pertinent factors; and second, to broaden the perspective of the third‐sector organizations beyond the traditional profile with which volunteers are commonly associated.     

Preliminary observations on habitat, support use and diet in two non-native primates in an urban Atlantic forest fragment: The capuchin monkey (Cebus sp.) and the common marmoset (Callithrix jacchus) in the Tijuca forest, Rio de Janeiro

Space is an important dimension of the ecological niche. Differentiation in the use of vertical strata of the forest is related to species body size, and explains in part species coexistence at a local scale. Large neotropical primates dwell in the canopy, moving quadrupedally on large branches, whereas smaller species leap between narrow branches in the understory. We tested this general pattern by observing focal individuals of the capuchin monkey (Cebus sp.) and the common marmoset (Callithrix jacchus), both non-native species, living in a forest fragment within the Rio de Janeiro city. Results were in accordance with the pattern for neotropical primates. Vertical use of the forest seems to be related with ecological interactions, especially for C. jacchus restricted to the lower strata due to aerial predation. Preliminary observations on diet corroborate the omnivory of Cebus and the gum feeding characteristic of C. jacchus. For Cebus sp. the exotic jack-fruit (Artocarpus heterophyllus) was the most important food item. Predation of both primates on vertebrates, especially by C. jacchus on passerines, could cause an uncommon impact on prey populations. In spite of anthropogenic impact, these non-native primates maintain the general pattern of habitat, support use and diet of the same or similar species in native neotropical communities.     

Large deviations of multiclass M/G/1 queues

Consider a multiclass M/G/1 queue where queued customers are served in their order of arrival at a rate which depends on the customer class. We model this system using a chain with states represented by a tree. Since the service time distribution depends on the customer class, the stationary distribution is not of product form so there is no simple expression for the stationary distribution. Nevertheless, we can find a harmonic function on this chain which provides information about the asymptotics of this stationary distribution. The associated h‐transformation produces a change of measure that increases the arrival rate of customers and decreases the departure rate thus making large deviations common. The Canadian Journal of Statistics 37: 327–346; 2009 © 2009 Statistical Society of Canada     

Point and interval estimators in a binomial-Poisson compound distribution

X ) and the overall sampling size (M). If the later is of Poisson type with parameter λ, a sequence of M=m Bernouilli trials originates a compound binomial-Poisson random variable. The estimator of the proportion p is studied within this framework, and a numerical approximation can be obtained for its sampling distribution for any sample size. Received: November 6, 1997; revised version: August 14, 2000     

Expressive Strategies in Drawing are Related to Age and Topic

In drawing, psychological mood can be denoted in a direct way (i.e., “literally”) through facial expression cues (e.g., a frowning face denotes sadness in a direct way), but it can also be connoted in an indirect way (i.e., “non-literally”) through figurative or non-figurative cues. This study examines how child and adult drawers selectively use literal and non-literal expressive strategies in accordance with the nature of the topic being depicted. In a between-subject design, 120 participants produced drawings of either a person or a house, in one of three versions: baseline, happy, and sad. The results indicated that drawers preferentially used literal expressive strategies for the person and non-literal strategies for the house. There was an increasing tendency between 7 and 11 years of age to express the drawn person’s mood non-literally in addition to literally. The positive correlation obtained between representational and expressive drawing ability suggests that enrichment of drawers’ graphic repertoire enhances their ability to draw expressively. Implications for clinical and educational practitioners are discussed.     

Preparing for business model change: the “pre-stage” finding

The purpose of this paper is to investigate managers’ initiatives in the context of an emergent technology and their effect on the business models of firms. Building on four case studies of organizations interested in using an emergent technology for commercial purposes, this study applies a process-based framework of business model change. The main finding is that managers’ initiatives occur in the context of a “pre-stage” of potential business model change, which includes processes of experimenting and learning. The pre-stage finding gives a better understanding of when change initiatives affect a business model and when they do not, allowing managers to adopt a more proactive behaviour and guide their organizations towards effective business model change. The main contribution of this paper is to suggest the inclusion of the pre-stage idea in research and practice, since it is an intermediary step in the process of business model change that has been overlooked.     

Star list chromatic number of planar subcubic graphs

A proper coloring of the vertices of a graph G is called a star-coloring if the union of every two color classes induces a star forest. The graph G is L-star-colorable if for a given list assignment L there is a star-coloring π such that π(v)∈L(v). If G is L-star-colorable for any list assignment L with |L(v)|≥k for all v∈V(G), then G is called k-star-choosable. The star list chromatic number of G, denoted by $\chi_{s}^{l}(G)$ , is the smallest integer k such that G is k-star-choosable. In this paper, we prove that every planar subcubic graph is 6-star-choosable.