Specification Sensitivity in Right-Tailed Unit Root Testing for Explosive Behavior

Right-tailed unit root tests have proved promising for detecting exuberance in economic and financial activities. Like left-tailed tests, the limit theory and test performance are sensitive to the null hypothesis and the model specification used in parameter estimation. This paper aims to provide some empirical guidelines for the practical implementation of right-tailed unit root tests, focussing on the sup ADF test of Phillips, Wu and Yu (2011), which implements a right-tailed ADF test repeatedly on a sequence of forward sample recursions. We analyze and compare the limit theory of the sup ADF test under different hypotheses and model specifications. The size and power properties of the test under various scenarios are examined in simulations and some recommendations for empirical practice are given. Empirical applications to the Nasdaq and to Australian and New Zealand housing data illustrate these specification issues and reveal their practical importance in testing.Unit root test, Mildly explosive process, Recursive regression, Size and power

Effects of Warm Up Intensity on Factors Related to Subsequent Performance of Submaximal Exercise

Introduction: Athletes often warm up (WU) prior to exercise to improve performance. However, there are no clear directives regarding the intensity of the WU that is most effective in improving physiological responses related to enhanced aerobic performance. Methods: Nine college-aged men (age, ht, mass, 20.6 yr, 1.7 m, 84.8 kg, respectively) performed WU of varying intensities, 60% ventilatory threshold (VT), 100%VT, and 120%VT prior to performing 5 min of steady state exercise at 80%VT on a cycle ergometer. O2 deficit, RPE, steady state heart rate (HRss), and steady state VO2 (VO2ss) were measured during the exercise bout. Results: There was a significant decrease in O2 deficit as WU intensity increased ((2,9)= 9.15, p = .002, 2=0.53) with the deficit being lowest after WU at 120%VT. RPE were significantly lower after WU at 120%VT than both 60% and 100%VT (=(2,9)=6.88, p=.007, 2=0.46). However, WU intensity did not significantly affect either HRss (F(2,9)=0.48, p=0.63) or VO2ss (F(2,9)=1.10, p=0.36) during the exercise bout. Conclusion: The findings suggest that a higher intensity WU improves factors related to improved aerobic performance, i.e. decreased O2 deficit and RPE, without adversely affecting factors that could lead to a decline in performance, i.e. increased HRss and VO2ss

Comparing Local Fitting to Other Automatic Smoothers

In a public service enterprise by Breiman and Peters (1991) various automatic smoothers, such as the supersmoother (SSMU), cross-validated smoothing splines (BART), delete-knot regression splines (DKS) and the cross-validated kernel smooth (KERNEL) were compared by simulation on a variety of sample sizes, noise levels and functions. The intention was to give practitioners guidelines when to use which type of smoother. The given work completes those simulations by including the increasingly popular local fitting approach, that was introduced to the statistical literature by Cleveland (1979). Fedorov et al. (1993) have modified the technique in order to take account possible misspecification bias, termed 'optimized moving local regression', and here we use an automated version (by crossvalidation) of it as given in Fedorov et al. (1994). (author's abstract)Series: Forschungsberichte / Institut für Statisti

Shengwen Wu, clarinet

Francis PoulencEric P. MandatEugene BozzaBela Kovac

From 'nothing' to inflation and back again

A procedure for solving Wheeler-DeWitt equation in Euclidean region, following step by step the construction of tunneling wave function in nonrelativistic quantum mechanics by Banks, Bender and Wu, is proposed. Solutions for a universe satisfying no-boundary condition and a universe created from 'nothing' are compared to the corresponding solutions for a particle in a two-dimensional potential well, and effects of indefiniteness of metric and zero energy in Wheeler-DeWitt equation are discussed.Comment: 8 pages, presented at the conference Relativity and Gravitation, 100 years after Einstein in Prague (Prague 2012

An explorative investigation into the warm-up practices of both professional and amateur rugby league players

PURPOSE: Rugby League (RL) players require high levels of speed, strength, power, agility and psychological readiness. Optimum preparation for performance via warm-up (WU) routines has been an area of research speculation in recent years. This study aimed to survey the WU protocols of professional and amateur RL players, to determine player’s perceptions of their featured WU procedures and to establish any significant differences in WU practices and perceptions between the two populations. METHODS: An online questionnaire was used to investigate 30 professional and 53 amateur players’ WU protocols and their perceptions behind their practices, providing both statistical and descriptive analysis. For a more in depth understanding into the practices and perceptions of the featured protocols, the questionnaire was followed up by two focus groups which included four participants in each (one professional group and one amateur). Raw data was produced from the focus groups which was then placed within higher-order themes and general dimensions. RESULTS: The questionnaire revealed a significant between-group difference for the duration of the WU’s between the two separate standards (P = 0.009). Professionals’ WU protocols were considerably longer in duration compared to the amateurs’ protocols; 67% of professional players performed WU routines for 15+ min whereas only 42% of amateur players claimed to WU for 15+ min. However, no between-group differences existed for protocols, perception variables, static stretching (SS) duration and similarity of the WU protocol (P > 0.05). The questionnaire also revealed the prevalence of SS; 83% of amateur participants and 90% of professional players claimed to perform SS during their WU. The focus group revealed that RL players’ protocols and perceptions of their regime are due to the influences of others such as coaches, strength and conditioning practitioners and physiotherapists and emphasises the importance the role such professionals play. CONCLUSIONS: The results showed that professional participants WU for a longer period in comparison to amateurs. The high prevalence of SS within RL WU protocols at both a professional and amateur standard was clearly apparent, contradicting the vast amount of literature that would advocate the removal of SS in sports requiring explosive power due to the associated links with decrements in performance. Most professional and amateur RL participants were discovered to perform SS for a duration that has been proven to impair desired physiological attributes. Furthermore, the study revealed the dynamic element of a WU is being consistently placed before SS, by both the professional and amateur domain, which has been previously linked to decreases in body temperature and associated mechanisms related mechanisms. Players associated that there WU practice was heavily influenced by RL coaches and associated practitioners. PRACTICAL APPLICTIONS: It is recommended that coaches, strength and conditioning practitioners and other key influential figures are educated on optimal evidence based WU procedures prior to prescription. Important aspects for consideration and education include WU duration, intensity, protocol order and SS elongation, volume and duration. Whilst it is important to link the research in WU to performance, practitioners should be mindful of changing regimes abruptly and the idiosyncratic nature of how athletes prefer to prepare physically and mentally

Determination of the forward slope in p pp~p and pˉ p\bar p~p elastic scattering up to LHC energy

In the analysis of experimental data on $p p$ (or $\bar p p$) elastic differential cross section it is customary to define an average forward slope $b$ in the form $\exp{(-b|t|)}$, where $t$ is the momentum transfer. Taking as working example the results of experiments at Tevatron and SPS, we will show with the help of the impact picture approach, that this simplifying assumption hides interesting information on the complex non-flip scattering amplitude, and that the slope $b$ is not a constant. We investigate the variation of this slope parameter, including a model-independent way to extract this information from an accurate measurement of the elastic differential cross section. An extension of our results to the LHC energy domain is presented in view of future experiments.Comment: 12 pages, 6 figures, to appear in EPJ