Sign Tests for Long-memory Time Series

This paper proposes sign-based tests for simple and composite hypotheses on the long-memory parameter of a time series process. The tests allow for nonstationary hypothesis, such as unit root, as well as for stationary hypotheses, such as weak dependence or no integration. The proposed generalized Lagrange multiplier sign tests for simple hypotheses on the long-memory parameter are exact and locally optimal among those in their class. We also propose tests for composite hypotheses on the parameters of ARFIMA processes. The resulting tests statistics have a standard normal limiting distribution under the null hypothesis.Publicad

A new class of distribution-free tests for time series models specification

The construction of asymptotically distribution free time series model specification tests using as statistics the estimated residual autocorrelations is considered from a general view point. We focus our attention on Box-Pierce type tests based on the sum of squares of a few estimated residual autocorrelations. This type of tests belong to the class defined by quadratic forms of weighted residual autocorrelations, where weights are suitably transformed resulting in asymptotically distribution free tests. The weights can be optimally chosen to maximize the power function when testing in the direction of local alternatives. The optimal test in this class against MA, AR or Bloomfield alternatives is a Box-Pierce type test based on the sum of squares of a few transformed residual autocorrelations. Such transformations are, in fact, the recursive residuals in the projection of the residual autocorrelations on a certain score function

Discussing a teacher MKT and its role on teacher practice when exploring data analysis

This article considers teacher knowledge in managing mathematically critical situations and the role of what can be termed a mathematical summary in the analysis of a teaching episode, viewed from the perspective of Mathematical Knowledge for Teaching (MKT). The analysis is based on an episode of content review, from a perspective which aims to understand the teacher’s logic rather than merely identify gaps in their knowledge. We discuss the importance of approaching mathematically critical situations in order to contribute to eradicating mathematical innumeracy (statistics) and to promote a kind of practice which is “mathematically demanding” as well as “pedagogically exciting”

How costumers’ way of life influence the value co-creation

Purpose: This article is a contribution to the understanding of how value arises in wellestablished markets, and under which circumstances actors integrate resources from different service ecosystems to generate value. To understand this phenomenon, it is fundamental to consider which practices are performed by customers to co-create value and how they do so. Design/Methodology/Approach: Using a qualitative approach, the study provides fresh empirical insight into well-established market processes of value creation. After a literature review an ethnographic approach was chosen in order to understand how co-creation processes occur in the empirical setting of an international restaurant chain. Several observations, conversations and semi-structured interviews were undertaken concerning the analysis of the topic under study. Findings: The results show that even in a well-established market, a provider must consider individual customers’ distinct needs, present in their daily practices, to be able to assist them in the value creation process. It is argued that the practice styles are the building blocks for prevailing ways of life that actors assume, according to the context in which they are, to integrate resources. Practical implications: The study includes implications for service providers of a wellfounded market for facilitating value co-creation along with customers and fulfils the need to better understand this phenomenon. Originality/Value: Recent studies call for empirical evidence on co-creation processes in mature markets, accordingly, this study brings an additional understanding on how actors, depending on the context, adopt different ways of life that require unique resources, which activate to achieve what they want, in order to establish room for co-creation.peer-reviewe

Nonparametric Tests for Conditional Symmetry in Dynamic Models

This article proposes omnibus tests for conditional symmetry around a parametric function in a dynamic context. Conditional moments may not exist or may depend on the explanatory variables. Test statistics are suitable functionals of the empirical process of residuals and explanatory variables, whose limiting distribution under the null is nonpivotal. The tests are implemented with the assistance of a bootstrap method, which is justified assuming very mild regularity conditions on the specification of the center of symmetry and the underlying serial dependence structure. Finite sample properties are examined by means of a Monte Carlo experiment.Publicad