Can portmanteau nonlinearity tests serve as general mis-specification tests?

A number of recent papers have employed the BDS test as a general test for mis-specification for linear and nonlinear models. We show that for a particular class of conditionally heteroscedastic models, the BDS test is unable to detect a common mis-specification. Our results also demonstrate that specific rather than portmanteau diagnostics are required to detect neglected asymmetry in volatility. However for both classes of tests reasonable power is only obtained using very large sample sizes.

Portmanteau model diagnostics and tests for nonlinearity: a comparative Monte Carlo study of two alternative methods

This paper employs an extensive Monte Carlo study to test the size and power of the BDS and close return methods of testing for departures from independent and identical distribution. It is found that the finite sample properties of the BDS test are far superior and that the close return method cannot be recommended as a model diagnostic. Neither test can be reliably used for very small samples, while the close return test has low power even at large sample sizes

Portmanteau plays.

Mode of access: Internet.

Testing against changing correlation

A test for time-varying correlation is developed within the framework of a dynamic conditional score (DCS) model for both Gaussian and Student t-distributions. The test may be interpreted as a Lagrange multiplier test and modified to allow for the estimation of models for time-varying volatility in the individual series. Unlike standard moment-based tests, the score-based test statistic includes information on the level of correlation under the null hypothesis and local power arguments indicate the benefits of doing so. A simulation study shows that the performance of the score-based test is strong relative to existing tests across a range of data generating processes. An application to the Hong Kong and South Korean equity markets shows that the new test reveals changes in correlation that are not detected by the standard moment-based test.

Bax and the 'Celtic North'

A feature of scholarship on Arnold Bax is his indebtedness, in his early works, to the Irish literary revival (particularly in the mythology-suffused works of 'AE' and early Yeats) and, in his later works, to the music of Jean Sibelius, and the relationship between these periods. I argue that this relationship, which I summarize by using Bax's portmanteau term of 'Celtic North', is underpinned by the stimulus of landscape, which, as well as being a means by which to return to the Romantic idea of the sublime, also provides a means by which Bax critiques the more modernist relationship with landscape that underpins the English pastoral school of the 1920s. Thus the 'Celtic North' is the antithesis to the English 'south land' of Vaughan Williams and others.

Les tests de causalité en variance entre deux séries chronologiques multivariées

Les modèles de séries chronologiques avec variances conditionnellement hétéroscédastiques sont devenus quasi incontournables afin de modéliser les séries chronologiques dans le contexte des données financières. Dans beaucoup d'applications, vérifier l'existence d'une relation entre deux séries chronologiques représente un enjeu important. Dans ce mémoire, nous généralisons dans plusieurs directions et dans un cadre multivarié, la procédure dévéloppée par Cheung et Ng (1996) conçue pour examiner la causalité en variance dans le cas de deux séries univariées. Reposant sur le travail de El Himdi et Roy (1997) et Duchesne (2004), nous proposons un test basé sur les matrices de corrélation croisée des résidus standardisés carrés et des produits croisés de ces résidus. Sous l'hypothèse nulle de l'absence de causalité en variance, nous établissons que les statistiques de test convergent en distribution vers des variables aléatoires khi-carrées. Dans une deuxième approche, nous définissons comme dans Ling et Li (1997) une transformation des résidus pour chaque série résiduelle vectorielle. Les statistiques de test sont construites à partir des corrélations croisées de ces résidus transformés. Dans les deux approches, des statistiques de test pour les délais individuels sont proposées ainsi que des tests de type portemanteau. Cette méthodologie est également utilisée pour déterminer la direction de la causalité en variance. Les résultats de simulation montrent que les tests proposés offrent des propriétés empiriques satisfaisantes. Une application avec des données réelles est également présentée afin d'illustrer les méthodes

Sur la validation des modèles de séries chronologiques spatio-temporelles multivariées

Dans ce mémoire, nous avons utilisé le logiciel R pour la programmation.

Contributions dans l'analyse des modèles vectoriels de séries chronologiques saisonnières et périodiques

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

Weaving the web - From myth to modernity

The discovery, development or invention of new objects and phenomena by humankind, requires a new set of words to be coined or adopted to describe it. This is also true of the Information Communication Technology (ICT) world. Words are not neutral, regardless of which dialect or language they occur in. They carry with them associations and connotations based on their previous applications and alliances, and augmented by their shapes, sounds, rhymes and rhythms. The subtext that word choice creates, while often not recognised or acknowledged, is important in considering how communication operates in, and shapes Information Technology (IT) environments. Many words that are now embedded in the ICT lexicon continue to be informed by these earlier meanings, some of which, in the English lexis, are drawn from myths. The vernacular of the ICT lexis reflects its openness to new ideas, the nature of its users, its English language roots and its Western cultural origins. This contributes to a particular communication style. But such lexis can prove problematic for non-English speaking background users and/or those from different cultures. As the ICT vocabulary continues to evolve, these language and cultural underpinnings are coming under challenge, suggesting a language and cultural future very different to the past. This in turn, will create a subtext that affects all users.

Testes de ajustamento de modelos em processos com longa dependência

Estudamos neste trabalho, o nível de significância empírico dos testes portmanteau baseados nas estatísticas propostas por Ljung e Box (1978), Monti (1994) e Pe˜na e Rodríguez (2002) nos processos ARFIMA(p; d; q). Consideramos o processo ARFIMA(p; d; q) nas situações adequadas para representar séries temporais com características de longa dependência. Para estimar o parâmetro de diferenciação d utilizamos os métodos de estimação propostos por Geweke e Porter-Hudak (1983), Reisen (1994), Robinson (1994) e Fox e Taqqu (1983).

Future trends in human resource management in emerging markets

In many ways the emerging markets represent something of a new frontier for academics and practitioners alike, or as one author puts it, ‘a significant topic of interest for a multitude of constituencies’ (Alkire, 2014: 334). The very term itself ‘emerging markets’ is something of a portmanteau one built on a series of layered insights garnered from several academic fields and multiple levels of analysis. Originally coined as a term in the 1980s, albeit with several earlier linked terminologies, this is an evolving and diverse literature. Inherent in its diversity lies a whole series of opportunities, encompassing the purely theoretical through to the methodological and the analytical. Capturing the essence of this in his Editorial in the inaugural edition of The International Journal of Emerging Markets, Akbar (2006) noted that from an academic perspective the emerging markets as a context for the creation and execution of a sustainable research agenda represent ‘a heterogeneous group of economies and societies’ and an ‘important testing ground for our existing theories, models and concepts of business and management’ affording those who focus on them as a research location the opportunity for ‘the development of new theoretical contributions in the field’. In this volume, we have sought to bring some systematics to this evolving literature dedicated to charting HRM in these emerging markets.