Quasi-linear PCA: low order spline's approach to non-linear principal components

Nonlinear Principal Components Analysis (PCA) addresses the nonlinearity problem by relaxing the linear restrictions on standard PCA. A new approach on this subject is proposed in this paper, quasi-linear PCA. Basically, it recovers a spline based algorithm designed for categorical variables and introduces continuous variables into the framework without the need of a discretization process. By using low order spline transformations the algorithm is able to deal with nonlinear relationships between variables and report dimension reduction conclusions on the nonlinear transformed data as well as on the original data in a linear PCA fashion. The main advantages of this approach are; the user do not need to care about the discretization process; the relative distances within each variables' values are respected from the start without discretization losses of information; low order spline transformations allow recovering the relative distances and achieving piecewise PCA information on the original variables after optimization. An example applying our approach to real data is provided below

Job polarisation: Capturing the effects of work organisation

This article critically challenges the findings and assumptions of mainstream job polarisation literature. Based on the European Working Conditions Survey data and on the Job Demand-Control model, which allows for capturing the organisational dimension of jobs, we examine the patterns and evolution of occupations in 22 European countries from 2005 to 2015. Instead of pervasive job polarisation, we observe a near-pervasive trend of upgrading job quality, suggesting that job polarisation may be caused by the undervaluation/devaluation of jobs low in the occupational hierarchy – not by computerisation-driven changes in work tasks. Indeed, only the former can explain the decrease in the number of low-quality jobs while the number of low-paid jobs increases. After documenting the relevance of firm-level organisational choices, we suggest that counteracting job polarisation requires, beyond meso-level collective bargaining, a public intervention that promotes participatory decision-making in firms.info:eu-repo/semantics/acceptedVersio

Declining autonomy at work in the EU and its effect on civic behaviour

The aim of this paper is to show that social benefits may accrue from work environments that support autonomous forms of work. Based on social psychology, economics and philosophy approaches, we argue that autonomy is a basic human need which, when satisfied, enhances civic behavior. Using individual data from the EWCS, we find evidence of the positive effect of work autonomy on volunteer work and political/trade union activities. Overall, work autonomy has decreased over the last fifteen years for all skill levels in the EU, though there are substantial differences between countries. Organizational practices that promote autonomy should be deliberately stimulated if civic participation is to be furthered.FC

The determinants of work autonomy and employee involvement: A multilevel analysis

Although work autonomy (WA) and employee involvement (EI) are often subsumed into a single construct in the literature, we argue that there is theoretical and empirical ground to meaningfully distinguish the two notions. To better understand a) the extent to which WA and EI are distinct constructs and b) the factors that explain their respective levels, we use the 2010 European Working Conditions Survey to build sound indexes of WA and EI, provide a picture of the level of both constructs in 31 European countries and analyse their predictors through multilevel structural models. The results show that WA and EI differ significantly in what concerns their macro-level but not micro-level predictors. Whereas union density and generalised trust strongly influence EI, only generalised trust impacts WA. Documenting that generalised trust as a macro-social trait is powerfully associated with organizational choices is a key contribution of the paper.info:eu-repo/semantics/acceptedVersio

Research-based spin-offs targeting the market for technologies: a conceptual model

DINÂMIA, Dezembro de 2009.This paper addresses the commercialisation decisions of research-based spin-off firms, focusing on the case of companies specialising in the production and sale of intellectual property - a model of entrepreneurial behaviour increasingly frequent in science-based fields, and that research-based spin-offs may be more prone to adopt given their specific characteristics. Combining insights from the economics of technological change and the strategic management of technology literature, we discuss the conditions that influence spin-offs ability to pursue with this strategy, and advance some theory-driven hypothesis regarding key factors that are likely to determine their choice - nature of knowledge, appropriability conditions, location and degree of control upon complementary assets and institutional setting of origin - and their impact upon firms’ decisions. We add to the still incipient research on this model of behaviour, as well as to recent research on the determinants of the commercialisation strategy of small technologyintensive firms.FC

Strategic partnerships in the renewable energy sector in Portugal

This paper focuses on the strategic partnerships established by firms operating in the renewable energy technologies sector in Portugal. The analysis aims at contributing to deepen the knowledge about the types and forms of partnerships in the renewables sector. The goal is to uncover the factors that explain the success of these partnerships and draw conclusions on the way they contributed to building a renewables cluster in Portugal.info:eu-repo/semantics/acceptedVersio

Statistical power analysis with microsoft excel: normal tests for one or two means as a prelude to using non-central distributions to calculate power

This article presents statistical power analysis (SPA) based on the normal distribution using Excel, adopting textbook and SPA approaches. The objective is to present the latter in a comparative way within a framework that is familiar to textbook level readers, as a first step to understand SPA with other distributions. The analysis focuses on the case of the equality of the means of two populations with equal variances for independent samples with the same size. This is the situation adopted as case 0 by Cohen (1988), a pioneer in the subject, to develop his set of tables and so, the present article can be seen as an introduction to Cohen's methodology applied to tests based on samples from normal populations. We also discuss how to extend the calculation to cases with other characteristics (cases 1 to 4), similarly to what Cohen proposes, as well as a brief discussion about the advantages and shortcomings of Excel. We teach mainly in the area of business and economics, which determines the scope of our analysis.info:eu-repo/semantics/publishedVersio

Strategic partnerships of the renewable energy firms in Portugal

This paper focuses on the strategic partnerships established by firms operating in the renewable energy technologies sector in Portugal. The analysis aims at contributing to deepen the knowledge about the types and forms of partnerships in the renewables sector. The goal is to uncover the factors which explain the success of these partnerships and draw conclusions on the way they contributed to building a renewables cluster in Portugal.FC

Describe all or just a few? The influence of verbal descriptors on Likert-type variables on items’ and scales’ distribution

The aim of this study is to examine whether and how the use of verbal descriptors at all categories or just at the extremes of 5-point Likert-type items influences the results. Each participant was requested to mark his/her level of agreement with 18 items concerning beliefs on mathematics, using one of the following forms: with verbal descriptors at all categories or just at the extremes. Respondents were found to use more intensively the extreme categories when only these were verbally described. However, these differences were not significant when using summated scales, except in case of severe skewness.info:eu-repo/semantics/publishedVersio

The effect of shape: Comparing different presentations of response

The aim of this field based work is to study in what measure different presentations of Likert-type items (including “continuous” options, i.e. marking the option on a straight line, with or without middle point and the use of all anchors vs extreme-only labels) induce different behaviours in items or scales distributions. In different areas of knowledge is necessary to know and explore indicators of attitude or motivation, in order to support the decision. To measure these non-measurable quantities, rating scales have been proposed, which intend to gather the “degree of affection” of an individual on a particular object or value. Several studies have evaluated and compared the behaviour of different rating scales. Some focus how to treat the items that compose the scales, others where the main goal is to analyse the scales' shape. As part of a wider project about perceptions of mathematics, four questionnaires were constructed: in the first two (A and B) the statements are evaluated by marking the response on a line segment (Visual Analogue Scale), labelled in the extreme and at the midpoint (A) or only at the extremes (B). In the third (C), Likert-type items with five labelled points are used (completely disagree, disagree, neither agree nor disagree, agree and totally agree), while in D only the extremes are labelled. We used theoretically-defined summated scales. The responses are compared at a scale level. The performance evaluation was made using location and shape measures, including robust variations.info:eu-repo/semantics/publishedVersio