A Test for the Presence of Central Bank Intervention in the Foreign Exchange Market With an Application to the Bank of Canada

We propose a general non-linear simultaneous equations framework for the econometric analysis of models of intervention in foreign exchange markets by central banks in response to deviations of exchange rates from target levels. We consider the instrumental variables estimation of possibly non-linear response functions and tests of intervention when the functional form may be non-linear, asymmetric, and may contain unknown shape parameters. The methodology applies techniques developed for testing in the presence of nuisance parameters unidentified under a null hypothesis to a nonlinear simultaneous equations model. We report the results of an empirical analysis of activity of the Bank of Canada, for the period from 1953-2006, with regard to the Canada-U.S. exchange rate, with changes in foreign reserves proxying for intervention activity. Nous proposons un cadre de référence général pour les équations non-linéaires simultanées s’appliquant à l’analyse économétrique de modèles d’intervention des banques centrales dans les marchés des devises étrangères, en réponse aux écarts des taux de change par rapport aux niveaux cibles. Nous prenons en considération l’estimation des variables instrumentales liées aux fonctions de réponses possiblement non-linéaires et aux tests en matière d’interventions lorsque la forme fonctionnelle peut être non linéaire, asymétrique et lorsqu’elle peut contenir des paramètres de forme inconnue. La méthodologie applique, à un modèle à équations simultanées non linéaires, des techniques élaborées pour effectuer des tests en présence de paramètres de nuisance non identifiés sous une hypothèse nulle. Nous présentons les résultats d’une analyse empirique des activités de la Banque du Canada, durant la période de 1953-2006, relativement au taux de change Canada-É.-U., les variations des réserves étrangères permettant les activités d’intervention.unidentified nuisance parameter, nonlinear simultaneous equations, foreign exchange reserves, policy reaction functions, paramètre de nuisance non identifié, équations simultanées non linéaires, réserves de change, fonctions de réaction de la politique

Dimension Reduction and Model Averaging for Estimation of Artists’ Age-Valuation Profiles

In hedonic regression models of the valuation of works of art, the age at which an artist produces a particular work, or an indicator variable for periods in his or her artistic career, is often found to have highly significant predictive value. Most existing results are based on regressions that pool large groups of painters. Although it is of interest to estimate such regressions for individual artists, the sample sizes are often inadequate for a model that would also include the large number of other relevant variables. We address this problem of inadequate degrees of freedom in individual artist regressions by using two statistical methods (model averaging and dimension reduction) to incorporate information from a potentially large number of predictor variables, allowing us to work with relatively small samples. We find that individual age-valuation profiles can differ substantially from general pooled profiles, suggesting that methods that are more responsive to the unique features of individual artists may provide better predictions of art valuations at auction. In hedonic regression models of the valuation of works of art, the age at which an artist produces a particular work, or an indicator variable for periods in his or her artistic career, is often found to have highly significant predictive value. Most existing results are based on regressions that pool large groups of painters. Although it is of interest to estimate such regressions for individual artists, the sample sizes are often inadequate for a model that would also include the large number of other relevant variables. We address this problem of inadequate degrees of freedom in individual artist regressions by using two statistical methods (model averaging and dimension reduction) to incorporate information from a potentially large number of predictor variables, allowing us to work with relatively small samples. We find that individual age-valuation profiles can differ substantially from general pooled profiles, suggesting that methods that are more responsive to the unique features of individual artists may provide better predictions of art valuations at auction.Dimension reduction, factor-augmented model, model averaging, réduction de dimension, modèle de facteur augmenté, moyenne de modèles

The effects of technology on making conjectures: linking multiple representations in learning iterations

Numerous studies have suggested that different technologies have different effects on students' learning of mathematics, particularly in facilitating students' graphing skills and preferences for representations. For example, there are claims that students who prefer algebraic representations can experience discomfort in learning mathematics concepts using computers (Weigand and Weller, 2001; Villarreal, 2000) whilst students using calculators preferred graphical representation (Keller and Hirsch, 1994). Although, arguably, the teaching of mathematics has traditionally centred more on procedural skills, it is possible that students' understandings, preferences and difficulties in relating different representations might be explained by analysing students' thought processes in terms of the making of conjectures. Within the topic of iteration, this study investigated how using graphical calculators, and PC-based graphing software changed A-level mathematics students' conjectures in relation to: 1) students' understanding of the concepts of iteration, and their discovery of the properties of particular iterations; 2) students' preferences for representations; and 3) the way the students express their conjectures. Students were observed tackling iteration questions using graphical calculators, and, later, graphing software. The students' written inferences were collected using two parallel worksheets and were subsequently analysed using a coding scheme developed based on previous studies in the literature, and focusing on students' conjectures as a unit of analysis. The investigation found similar results to those of previous studies in terms of graphing difficulty, linking different representations and preferences for representations. However, the results also hinted that the computer positively influences students' understanding of iteration and their movement between representations more than the graphical calculator; and this possibility requires further research

Linking multiple representations in exploring iterations: does change in technology change students' conjectures?

This study investigates changes in conjectures of four typical students when they are using different kinds of technologies, particularly in relation to their preferences for representations and the way they express their conjectures in understanding the concept and properties of iteration. The first stage of the research was conducted using pen and paper (PP) with graphical calculator (GC) in a classroom while the second stage used PP with graphical software (GS) in a laboratory. The findings suggest, with important caveats, that different technologies significantly influence the students' preferences for representations. Also, this study shows that students' conjectures can be an effective unit of analysis in researching students' understanding of iteration and preferences for representations

'There's more than meets the eye': analysing verbal protocols, gazes and sketches on external mathematical representations

When learners are asked to verbalise their thoughts about multiple mathematical representations, some researchers are left to analyse utterances based on video records of activity which may have ambiguous signifiers. They are also faced with post hoc analysis of paper-based worksheets, in which temporal order has to be guessed. In this paper, attempts to minimise such methodological problems by means of recent technologies such as eye-tracking, tablet PC screen capture, digital video cameras and the latest video analysis tools are illustrated in the context of a study of the effect of varying representational instantiations on learners' problem-solving strategies

The Assassin Bug \u3ci\u3eZelus Luridus\u3c/i\u3e (Heteroptera: Reduviidae) in Michigan\u27s Upper Peninsula

(excerpt) On 17 July 1992, an assassin bug (Zelus luridus Stal) was flushed from the stomach of a smallmouth bass (Micropterus dolomieu) collected in West Long Lake of the University of Notre Dame Environmental Research Center, Gogebic County, Michigan

Poetic Individuality in Clare, Hopkins, and Edward Thomas

John Clare, Gerard Manley Hopkins, and Edward Thomas form a trio of disparate yet tantalisingly related poets. What distinguishes them also conjoins them: the desire, in Hopkins’ words, to invest their poetry with ‘an individualising touch’. The poetic achievement of all three is animated by the effort to discover an idiom that answers to the pressure of a unique cast of mind, feeling, and vision of experience. All three poets stand consciously apart from their period. They articulate a recurrent counter-voice in English poetry of the nineteenth and early twentieth centuries, grounded in an effort to imbue poetic language with an acutely personal bearing. The Introduction establishes the interrelation of their personal and poetic individuality, exploring the way their poems formulate and embody shared aims. Clare once enthused over Keats’s description in Isabella of an eye ‘Striving to be itself’. The phrase gets purchase on the spirit of embattled innovation that the three chapters on Clare’s poetry locate in his language. The first seeks to characterise the haphazard ingenuity of Clare’s style, pursuing his trust in a brand of seemingly improvisational inventiveness as a means of discovering new modes of expression. Chapter 2 concentrates on the more controlled aspects of Clare’s experimentalism, attending to his poems’ twinning of actual and literary discovery. Chapter 3 focuses more explicitly on the disarmingly personal nature of Clare’s poetry, thinking about its strange marriages of personal fervour and literary archetype. Hopkins insisted on ‘originality’ as a ‘condition of poetic genius’; but his poetry is alert to originality’s costs as well as its virtues. The concern of Chapter 4 is with how Hopkins’ valorisation of distinctiveness sits in tension with his wariness of ‘Parnassian’ – the quality of ‘being too so-and-so-all over-ish’; it contends that Hopkins is most himself at his most unpredictable. Chapter 5 extends an emphasis on Hopkins’ blend of craft and spontaneity, and the intricacy and fervour of his expression of feeling, into a consideration of the rich presence his poetry affords to the heart. Chapter 6 attends to the ways in which Hopkins’ nerviness about the potentially alienating qualities of his individual style feeds back into the distinctive tenor of his voice. Thomas thought that ‘nothing so well represents […] singularity as style’. The first chapter on his poems explores takes off from T. S. Eliot’s notion of the ‘auditory imagination’ to explore the fusion of poetic and personal ‘singularity’ in Thomas’s harnessing of the postures of speech, and experimentation with the forms and rhythms of folk song. A large part of the individuality of Thomas’s style owes to the intricacy and tenacity of his syntax, and Chapter 8 explores the way in which his poetry’s distinctive voice arises out of an effort to trace the contours of thought and feeling. A final chapter devotes itself to the way in which, for all his idiosyncrasy, Thomas, like Clare and Hopkins, strives to achieve intimacy with a reader, contending that his best poems often invite us into the confidence of a personality that remains finally elusive. A coda emphasises the inventiveness and personal candour that unites the three poets’ language

Learners' strategies with multiple representations

This empirical study investigated how varied instantiations of mathematical representations influenced learners' strategies. The analysis took into account gazes, utterances, actions and writings of 18 learners performing 3 tasks using static, dynamic, and interactive instantiations. Results show a variation in frequencies of strategies that the participants of the study employed for using multiple representations. This indicates that varying instantiations of multiple representations influences learners' strategies