On Testing for the Nullity of Some Skewness Coefficients

Ngatchou-Wandji, Joseph

doi:10.1111/j.1751-5823.2006.tb00160.x

Cited by 10 publications

(14 citation statements)

References 42 publications

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“…with standard deviation. For gaining an interesting insight into skewness estimation, the reader may refer to [27]. Contrary to pure ELM events, the distribution of τ ELM for ELMs followed by STEs in high f ST E JET ILW plasmas (figure 5(e)) follows a more symmetric distribution.…”

Section: Elm Duration and Slow Transport Eventsmentioning

confidence: 99%

Correlation analysis for energy losses, waiting times and durations of type I edge-localized modes in the Joint European Torus

et al. 2017

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Abstract. Several important ELM control techniques are in large part motivated by the empirically observed inverse relationship between average ELM energy loss and ELM frequency in a plasma. However, to ensure a reliable effect on the energy released by the ELMs, it is important that this relation is verified for individual ELM events. Therefore, in this work the relation between ELM energy loss (W ELM ) and waiting time (∆t ELM ) is investigated for individual ELMs in a set of ITER-like wall plasmas in JET. A comparison is made with the results from a set of carbon-wall and nitrogenseeded ITER-like wall JET plasmas. It is found that the correlation between W ELM and ∆t ELM for individual ELMs varies from strongly positive to zero. Furthermore, the effect of the extended collapse phase often accompanying ELMs from unseeded JET ILW plasmas and referred to as the slow transport event (STE) is studied on the distribution of ELM durations, and on the correlation between W ELM and ∆t ELM . A high correlation between W ELM and ∆t ELM , comparable to CW plasmas is only found in nitrogen-seeded ILW plasmas. Finally, a regression analysis is performed using plasma engineering parameters as predictors for determining the region of the plasma operational space with a high correlation between W ELM and ∆t ELM .

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Section: Elm Duration and Slow Transport Eventsmentioning

confidence: 99%

Correlation analysis for energy losses, waiting times and durations of type I edge-localized modes in the Joint European Torus

et al. 2017

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“…In Ngatchou-Wandji (2006), the level and power of several tests for skewness are derived and compared by simulation studies, including Test 1 and Test 2.…”

Section: Level and Power Comparisons For Distribution-free Tests For mentioning

confidence: 99%

“…We will find effective distribution-free tests and confidence intervals based onγ r =Ŝ r /R r . Ngatchou-Wandji (2006) studies the level and power of other tests based on several skewness coefficients, including the Studentized version ofŜ r .…”

Section: Introductionmentioning

confidence: 99%

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Inference for quantile measures of skewness

Staudte

2014

TEST

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Given a location-scale family generated by a distribution with smooth positive density, the aim is to provide distribution-free tests and confidence intervals for a skewness coefficient determined by three quantiles. It is the Bowley-Hinkley ratio S r /R r , where S r = x r + x 1−r − 2x 0.5 is the sum of two symmetric quantiles minus twice the median, and R r = x 1−r −x r is the r th interquantile range. Here, 0 < r < 0.5 is to be chosen and fixed. The sample version of this ratio depends only on three order statistics and is the basis for tests and confidence intervals. It is shown that the variance stabilized version of this statistic leads to more powerful tests than the Studentized version of the sample version of S r . Sample sizes required to obtain accurate coverage of confidence intervals with a prespecified width are provided.

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“…For more instances, we refer the reader to [5]. Furthermore, Ngatchou-Wandji [10] has pointed out that, in economy and finance for example, it is sometimes desirable to know whether a distribution is skewed or not. It may thus be interesting to test for skewness of distributions.…”

Section: Introductionmentioning

confidence: 99%

A Bootstrap Test for Symmetry based on Quantiles

Zardasht¹

2016

HJMS

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In this paper, we construct a nonparametric test for the symmetry assumption of an underling distribution based on the sample quantiles. Bootstrap re-sampling from a symmetric empirical distribution function is used to obtain the p-value of the test. The power of the new test statistic is compared with some well-known symmetry tests using a simulation study. The results show that the proposed test preserves its level and it has reasonable power properties on the family of distribution evaluated.

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On Testing for the Nullity of Some Skewness Coefficients

Cited by 10 publications

References 42 publications

Correlation analysis for energy losses, waiting times and durations of type I edge-localized modes in the Joint European Torus

Correlation analysis for energy losses, waiting times and durations of type I edge-localized modes in the Joint European Torus

Inference for quantile measures of skewness

A Bootstrap Test for Symmetry based on Quantiles

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