A Simple Asymptotic Analysis of Residual-Based Statistics

What s the asymptotic null distribution of a rank-based serial autocorrelation test applied to residuals of an estimated GARCH model?What s the limiting distribution of estimated ACD parameters applied to the residuals of some first-stage modelling procedure?This paper addresses the often occurring situation in econometrics of applying standard statistics to residuals instead of innovations.The paper provides a simple and unified way of calculating the necessary adjustment in the limiting distribution, be it of tests or estimators. On the technical side, we also provide a novel approach to this problem using Le Cam s theory of convergence of experiments (in this paper restricted to Gaussian shift experiments).The resulting formula is simple and the regularity conditions required fairly minimal.Numerous examples show the strength and wide applicability of our approach.statistics;estimation;ranking

The use and effectiveness of behavioural modification techniques in achieving and maintaining normal weight and fitness – the lifestyle changes for adults in Cyprus

BACKGROUND and AIM: Research showed that behavioural modification techniques were the most effective way to achieve and maintain a healthy weight compared to diet and exercise alone. If behavioural modification was the most effective technique, then at least the two thirds of the candidates (Weight Loss Candidate with Behaviour Modification-WLCB) who used the specific behavioural modification techniques regarding eating and physical activity would achieve a weight loss of average ½ -1kg per week for the 18 weeks of the treatment and then maintain it or continue to lose after treatment termination with a total treatment period of 36 weeks. The treatment was efficient and long-lasting compared to the control candidates who followed a diet plan only. Furthermore, if the use of behavioural modification was the most effective way for diet and exercise, then the weight loss and maintenance would be more efficient and long-lasting. The principal aim of this project was to develop behaviour modification techniques (protocol and guidelines) in order to promote effective weight management for sedentary and active Cypriot adults, concentrating on nutrition and exercise. STUDY DESIGN: The study was quantitative and qualitative in nature using an action research approach. Furthermore, it was observational and longitudinal using structured methods and a representative sample of adults 19-50 years of age is investigated for 36 weeks. METHODS: Anthropometric data and health and diet history were taken using standard methods from 315 (the control and intervention group (1:1) Cypriot adults from rural and urban areas. Individualised diet plans, personalised physical activities as well as behavioural modification parameters were assessed with the aid of a questionnaire, interview, food and exercise diary and behavioural checklist. Obesity and overweight were defined using the current International Obesity Task Force definition. The validated questionnaires for Physical Activity (IPAQ) and the nutritional assessment (National Integrated Health Associates) were used for initial assessment and the behavioural checklists were used for the follow up. Behavioural checklists were completed by the candidates on a bi-weekly basis along with the food and exercise diary. The questionnaire reliability (test-retest), internal consistency and ability to differentiate obese vs. normal-weight adult behaviours were tested using a pilot population of 50 adults not enrolled in a formal weight loss programme. Its reliability (checklists, food and exercise diary) and predictive validity were tested using a selective population: 265 adults of the observational group enrolled in behavioural modification treatment vs. diet. OBJECTIVES OF THE STUDY: Τhe objectives of the research were a) The study of every aspect of weight management and thus be capable of making suggestions for the development of guidelines and protocols for behavioural modification to health professionals working with the public. b) The identification and adjustment of eating and exercise behaviour related to body weight in order to achieve an efficient weight management in Cypriot overweight/obese adults. c) The evaluation of the effectiveness of the modest lifestyle changes in weight management induced by short-term energy/calorie restriction and behaviour modification in overweight and obese Greek Cypriots with Body Mass Index (BMI) above 25 or 30 respectively, or body weight 20% or above of Ideal Body weight (IBW), or body fat above normal levels. d) The development of education and counselling protocols and guidelines for professionals for weight management protocols based on the Mediterranean Diet and the eating and exercise habits of Cypriot Adults. e) The implementation of the protocols to intervention groups in order to identify the efficiency. OUTCOMES: The outcomes of the project was the development of an education and counselling protocol/manual which included teaching tools and guidelines for professionals for weight management with the title “Protocol and Guidelines for professional users for weight management for Adults: assessment, categorization, therapy/ follow up of overweight and obesity”. The development of an eating behaviour and physical activity protocol/manual based on the Mediterranean Diet and the demonstrated eating and exercise habits of Cypriot Adults can be used by the stakeholders and the public for efficient and effective weight management. RESULTS: The average length of weight loss treatment was 18 weeks for the intervention and the control groups, and the average weight loss for the intervention group was 11.96kg (t-test, p-value ≤ 0.001) and for the control group was 5.56kg (t-test, p-value≤ 0.002). During the 18 weeks of the maintenance period the 50% of the intervention group continued to lose while, an additional 48% of them maintained the weight and only 2% of them gained weight. CONCLUSIONS: To conclude, the prevalence of obesity worldwide has reached epidemic proportions. Physical inactivity and poor diet have been identified as primary contributors to the leading causes of death in developed countries including Cyprus. It is unfortunate that more emphasis is given to calorie restriction dieting rather than behavioural modification for diet and physical activity in achieving and maintaining weight loss. The fact is that incorporating appropriate behavioural modification techniques for diet and sufficient physical activity into one’s life is an essential component of achieving a healthy body weight. The research project aimed at developing a behavioural approach and behavioural modification techniques for the treatment of obesity and weight management adjusted to the needs of the Cypriot adult population. The difference of this approach underlines the emphasis that has to be given to the follow-up programme for the maintenance of the weight loss through behavioural modification. This approach evolved from the environmental control of eating behaviour to a broader approach characterized by systematic manipulation of all factors associated with eating and exercise patterns. The need for the project derives from the fact that obesity is a chronic condition with a substantial potential for relapse; therefore long–term treatments are needed. The expected outcomes of this project are the development of guidelines and protocols to be used by health professionals. The ultimate goal is the reduction of the obesity epidemic in Cyprus

A Simple Asymptotic Analysis of Residual-Based Statistics

What s the asymptotic null distribution of a rank-based serial autocorrelation test applied to residuals of an estimated GARCH model?What s the limiting distribution of estimated ACD parameters applied to the residuals of some first-stage modelling procedure?This paper addresses the often occurring situation in econometrics of applying standard statistics to residuals instead of innovations.The paper provides a simple and unified way of calculating the necessary adjustment in the limiting distribution, be it of tests or estimators. On the technical side, we also provide a novel approach to this problem using Le Cam s theory of convergence of experiments (in this paper restricted to Gaussian shift experiments).The resulting formula is simple and the regularity conditions required fairly minimal.Numerous examples show the strength and wide applicability of our approach.

Forecasting Exchange-Rates via Local Approximation Methods and Neural Networks

There has been an increased number of papers in the literature in recent years, applying several methods and techniques for exchange - rate prediction. This paper focuses on the Greek drachma using daily observations of the drachma rates against four major currencies, namely the U.S. Dollar (USD), the Deutsche Mark (DM), the French Franc (FF) and the British Pound (GBP) for a period of 11 years, aiming at forecasting their short-term course by applying local approximation methods based on both chaotic analysis and neural networks.Key Words: Exchange Rates, Forecasting, Neural Networks

Object Clitic production in monolingual and bilingual children with Specific Language Impairment: A comparison between elicited production and narratives

Abstract Pronominal clitics are sensitive to both morphosyntax and discourse. Problems in clitic use could therefore stem from morphosyntactic or discourse management problems in children with SLI. Previous studies focused on 3rd person clitic use identifying morphosyntactic problems. We compare 1st with 3rd person clitic elicitation by monolingual and bilingual children with SLI to examine whether perspective-switching in the same task would affect performance. Elicited 3rd person clitics were further compared with clitic use in narratives to investigate the role of richer discourse context in clitic production. Perspective-taking was independently examined with first- and second-order Theory of Mind tasks. Bilingual were more accurate than monolingual children with SLI in 1st person clitics, in the use of unambiguous clitics in narratives and in second-order ToM reasoning. We conclude that bilingualism seems to enhance SLI children’s discourse use and perspective-taking strategies which, in turn, improve their use of clitics in context-sensitive conditions.</jats:p

Reference maintenance in the narratives of Albanian–Greek and Russian–Greek children with Developmental Language Disorder: A study on crosslinguistic effects

Although a considerable number of studies have shown D(eterminer) elements, i.e. determiners and pronominal clitics, to be particularly vulnerable to impairment in monolingual children with Developmental Language Disorder (DLD), little is known about the use of appropriate or/and grammatically correct referring expressions in the children’s narrative production. Grammars of languages that differ in the way they encode and realize their D system may be viewed as the ideal context to disentangle the contribution of language (L1) transfer and morpho-syntactic impairment to reference use in the L2. The aim of the current study is to examine L1 effects in the use of referring expressions of 5- to 11-year-old Albanian–Greek and Russian–Greek children with DLD, along with typically developing (TD) bilingual groups speaking the same language pairs when maintaining reference to characters in their narratives. The three languages differ in their D elements, since Albanian and Greek have morphologically rich D systems in contrast to Russian, which lacks a definiteness distinction. Children produced oral narratives in Greek by using the Greek versions of two stories ( Cat and Dog) which have been designed within the Multilingual Assessment Instrument for Narratives (MAIN) tool of the COST Action IS0804. Results show that the groups did not differ in referential appropriateness. Regarding grammatical correctness, both groups with DLD produced more ungrammatical forms than TD children, while Russian–Greek children with DLD produced more ungrammatical article-less NPs than the other groups. The overall results reflect the joint contribution of language impairment and L1-specific typological properties in the definite forms used for character maintenance by bilingual children with DLD.</jats:p

Understanding the threats posed by non-native species: public vs. conservation managers.

Public perception is a key factor influencing current conservation policy. Therefore, it is important to determine the influence of the public, end-users and scientists on the prioritisation of conservation issues and the direct implications for policy makers. Here, we assessed public attitudes and the perception of conservation managers to five non-native species in the UK, with these supplemented by those of an ecosystem user, freshwater anglers. We found that threat perception was not influenced by the volume of scientific research or by the actual threats posed by the specific non-native species. Media interest also reflected public perception and vice versa. Anglers were most concerned with perceived threats to their recreational activities but their concerns did not correspond to the greatest demonstrated ecological threat. The perception of conservation managers was an amalgamation of public and angler opinions but was mismatched to quantified ecological risks of the species. As this suggests that invasive species management in the UK is vulnerable to a knowledge gap, researchers must consider the intrinsic characteristics of their study species to determine whether raising public perception will be effective. The case study of the topmouth gudgeon Pseudorasbora parva reveals that media pressure and political debate has greater capacity to ignite policy changes and impact studies on non-native species than scientific evidence alone

RAS mutation status predicts survival and patterns of recurrence in patients undergoing hepatectomy for colorectal liver metastases.

ObjectiveTo determine the impact of RAS mutation status on survival and patterns of recurrence in patients undergoing curative resection of colorectal liver metastases (CLM) after preoperative modern chemotherapy.BackgroundRAS mutation has been reported to be associated with aggressive tumor biology. However, the effect of RAS mutation on survival and patterns of recurrence after resection of CLM remains unclear.MethodsSomatic mutations were analyzed using mass spectroscopy in 193 patients who underwent single-regimen modern chemotherapy before resection of CLM. The relationship between RAS mutation status and survival outcomes was investigated.ResultsDetected somatic mutations included RAS (KRAS/NRAS) in 34 (18%), PIK3CA in 13 (7%), and BRAF in 2 (1%) patients. At a median follow-up of 33 months, 3-year overall survival (OS) rates were 81% in patients with wild-type versus 52.2% in patients with mutant RAS (P = 0.002); 3-year recurrence-free survival (RFS) rates were 33.5% with wild-type versus 13.5% with mutant RAS (P = 0.001). Liver and lung recurrences were observed in 89 and 83 patients, respectively. Patients with RAS mutation had a lower 3-year lung RFS rate (34.6% vs 59.3%, P &lt; 0.001) but not a lower 3-year liver RFS rate (43.8% vs 50.2%, P = 0.181). In multivariate analyses, RAS mutation predicted worse OS [hazard ratio (HR) = 2.3, P = 0.002), overall RFS (HR = 1.9, P = 0.005), and lung RFS (HR = 2.0, P = 0.01), but not liver RFS (P = 0.181).ConclusionsRAS mutation predicts early lung recurrence and worse survival after curative resection of CLM. This information may be used to individualize systemic and local tumor-directed therapies and follow-up strategies

Structural Change in (Economic) Time Series

Methods for detecting structural changes, or change points, in time series data are widely used in many fields of science and engineering. This chapter sketches some basic methods for the analysis of structural changes in time series data. The exposition is confined to retrospective methods for univariate time series. Several recent methods for dating structural changes are compared using a time series of oil prices spanning more than 60 years. The methods broadly agree for the first part of the series up to the mid-1980s, for which changes are associated with major historical events, but provide somewhat different solutions thereafter, reflecting a gradual increase in oil prices that is not well described by a step function. As a further illustration, 1990s data on the volatility of the Hang Seng stock market index are reanalyzed.Comment: 12 pages, 6 figure