The question of how to choose a copula model that best fits a given dataset is a predominant limitation of the copula approach, and the present study aims to investigate the techniques of goodness-of-fit tests for mul...The question of how to choose a copula model that best fits a given dataset is a predominant limitation of the copula approach, and the present study aims to investigate the techniques of goodness-of-fit tests for multi-dimensional copulas. A goodness-of-fit test based on Rosenblatt＇s transformation was mathematically expanded from two dimensions to three dimensions and procedures of a bootstrap version of the test were provided. Through stochastic copula simulation, an empirical application of historical drought data at the Lintong Gauge Station shows that the goodness-of-fit tests perform well, revealing that both trivariate Gaussian and Student t copulas are acceptable for modeling the dependence structures of the observed drought duration, severity, and peak. The goodness-of-fit tests for multi-dimensional copulas can provide further support and help a lot in the potential applications of a wider range of copulas to describe the associations of correlated hydrological variables. However, for the application of copulas with the number of dimensions larger than three, more complicated computational efforts as well as exploration and parameterization of corresponding copulas are required.展开更多
In cognitive radio networks,spectrum sensing under circumstances of dynamically varying noise and lacking prior information is a key challenge to the conventional spectrum sensing algorithms.Since the necessary inform...In cognitive radio networks,spectrum sensing under circumstances of dynamically varying noise and lacking prior information is a key challenge to the conventional spectrum sensing algorithms.Since the necessary information is rather difficult to obtain practically,most existing spectrum sensing methods are fettered in applications.Motivated by these,in this paper,a Frequency domain Goodness of Fit Test(FGoF)based spectrum sensing method is proposed.The FGoF makes full use of underlying information in Guard-Bands and the advantages of GoF test works for any distribution.Analytical and simulated results show that the FGoF is a robust spectrum sensing method in cognitive radio with the inherent advantages of invulnerability to dynamically varying noise.展开更多
The logistic regression model has been become commonly used to study the association between a binary response variable;it is widespread application rests on its easy application and interpretation. The subject of ass...The logistic regression model has been become commonly used to study the association between a binary response variable;it is widespread application rests on its easy application and interpretation. The subject of assessment of goodness-of-fit in logistic regression model has attracted the attention of many scientists and researchers. Goodness-of-fit tests are methods to determine the suitability of the fitted model. Many of methods proposed and discussed for assessing goodness-of fit in logistic regression model, however, the asymptotic distribution of goodness-of-fit statistics are less examine, it is need more investigated. This work, will focus on assessing the behavior of asymptotic distribution of goodness-of-fit tests, also make comparison between global goodness-of-fit tests, and evaluate it by simulation.展开更多
Background:Physicalfitness in childhood and adolescence is associated with a variety of health outcomes and is a powerful marker of current and future health.However,inconsistencies in tests and protocols limit interna...Background:Physicalfitness in childhood and adolescence is associated with a variety of health outcomes and is a powerful marker of current and future health.However,inconsistencies in tests and protocols limit international monitoring and surveillance.The objective of the study was to seek international consensus on a proposed,evidence-informed,Youth Fitness International Test(YFIT)battery and protocols for health monitoring and surveillance in children and adolescents aged 618 years.Methods:We conducted an international modified Delphi study to evaluate the level of agreement with a proposed,evidence-based,YFIT of core health-relatedfitness tests and protocols to be used worldwide in 6-to 18-year-olds.This proposal was based on previous European and North American projects that systematically reviewed the existing evidence to identify the most valid,reliable,health-related,safe,and feasiblefitness tests to be used in children and adolescents aged 618 years.We designed a single-panel modified Delphi study and invited 216 experts from all around the world to answer this Delphi survey,of whom one-third are from low-to-middle income countries and one-third are women.Four experts were involved in the piloting of the survey and did not participate in the main Delphi study to avoid bias.We pre-defined an agreement of 80%among the expert participants to achieve consensus.Results:We obtained a high response rate(78%)with a total of 169fitness experts from 50 countries and territories,including 63 women and 61 experts from low-or middle-income countries/territories.Consensus(>85%agreement)was achieved for all proposed tests and protocols,supporting the YFIT battery,which includes weight and height(to compute body mass index as a proxy of body size/composition),the 20-m shuttle run(cardiorespiratoryfitness),handgrip strength,and standing long jump(muscularfitness).Conclusion:This study contributes to standardizingfitness tests and protocols used for research,monitoring,and surveillance across the world,which will allow for future data pooling and the development of international and regional sex-and age-specific reference values,health-related cut-points,and a global picture offitness among children and adolescents.展开更多
Regression estimates are biased when potential confounders are omitted or when there are other similar risks to validity.The instrumental variable(IV)method can be used instead to obtain less biased estimates or to st...Regression estimates are biased when potential confounders are omitted or when there are other similar risks to validity.The instrumental variable(IV)method can be used instead to obtain less biased estimates or to strengthen causal inferences.One key assumption critical to the validity of the IV method is the exclusion assumption,which requires instruments to be correlated with the outcome variable only through endogenous predictors.The chi-square test of model fit is widely used as a diagnostic test for this assumption.Previous simulation studies assessed the power of this diagnostic test only in situations with strong violations of the exclusion assumption.However,low to moderate levels of assumption violation are not uncommon in reality,especially when the exclusion assumption is violated indirectly.In this study,we showed through Monte Carlo simulations that the chi-square model fit test suffered from a severe lack of power(<30%)to detect violations of the exclusion assumption when the level of violation was of typical size,and the IV causal inferences were severely inaccurate and misleading in this case.We thus advise using the IV method with caution unless there is a chance for thorough assumption diagnostics,like in meta-analyses or experiments.展开更多
A test statistic is proposed to perform the goodness-of-fit test in the unbinned maximum likelihood fit. Without using a detailed expression of the efficiency function, the test statistic is found to be strongly corre...A test statistic is proposed to perform the goodness-of-fit test in the unbinned maximum likelihood fit. Without using a detailed expression of the efficiency function, the test statistic is found to be strongly correlated with the maximum likelihood function if the efficiency function varies smoothly. We point out that the correlation coefficient can be estimated by the Monte Carlo technique. With the established method, two examples are given to illustrate the performance of the test statistic.展开更多
This study is undertaken to apply a bootstrap method of controlling the false discovery rate （FDR） when performing pairwise comparisons of normal means. Due to the dependency of test statistics in pairwise compariso...This study is undertaken to apply a bootstrap method of controlling the false discovery rate （FDR） when performing pairwise comparisons of normal means. Due to the dependency of test statistics in pairwise comparisons, many conventional multiple testing procedures can＇t be employed directly. Some modified pro- cedures that control FDR with dependent test statistics are too conservative. In the paper, by bootstrap and goodness-of-fit methods, we produce independent p-values for pairwise comparisons. Based on these indepen- dent p-values, plenty of procedures can be used, and two typical FDR controlling procedures are applied here. An example is provided to illustrate the proposed approach. Extensive simulations show the satisfactory FDR control and power performance of our approach. In addition, the proposed approach can be easily extended to more than two normal, or non-normal, balance or unbalance cases.展开更多
<p> <span style="font-family:Verdana;">To address the drawbacks of the traditional Parker test in multivariate linear</span><span style="font-family:;" "=""> ...<p> <span style="font-family:Verdana;">To address the drawbacks of the traditional Parker test in multivariate linear</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">models:</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">the process is cumbersome and computationally intensive,</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">we propose a new heteroscedasticity test.</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">A new heteroskedasticity test is proposed using the fitted values of the samples as new explanatory variables, reconstructing the regression model, and giving a new heteroskedasticity test based on the significance test of the coefficients, it is also compared with the existing Parker test which is improved using the principal component idea. Numerical simulations and empirical analyses show that the improved Parker test with the fitted values of the samples proposed in this paper is superior.</span> </p>展开更多
In this paper, a new statistics for testing two samples coming from the same population is derived from a simple linear model with an artificial parameter. Its limit distribution is a chi-squared distribution with 2 d...In this paper, a new statistics for testing two samples coming from the same population is derived from a simple linear model with an artificial parameter. Its limit distribution is a chi-squared distribution with 2 degrees of freedom under null hypothesis and the limit distribution is a noncentral chi-squared distribution with 2 degrees of freedom under certain sequence of alternative hypothesis. Finally, we make power comparison with other tests on two samples, especially, with Smirnov statistics.展开更多
Background: Physical fitness tests are widely used to assess endurance,sprint ability,coordination and/or strength.The objective of the present study was to analyze the degree to which the results of the Bundeswehr Ba...Background: Physical fitness tests are widely used to assess endurance,sprint ability,coordination and/or strength.The objective of the present study was to analyze the degree to which the results of the Bundeswehr Basis Fitness Test(BFT)–a physical fitness test comprising a sprint test(11×10-m shuttle test),a flexed-arm hang test and a 1000-m run–are consistent with the output measured during a bicycle ergometer test.The number of false-positive and falsenegative results with regard to the assessment of physical fitness were also examined.Methods: As part of a retrospective study,health assessments from 323 reenlistment examinations were evaluated regarding the output measured during a bicycle ergometer test and compared with the BFT results of the candidates.Results: Overall,a good correlation was shown between the bicycle ergometer test results and the results achieved in the BFT disciplines.All three disciplines of the BFT showed a highly significant correlation with the relative output achieved during the bicycle ergometer test(P<0.001),and also,the overall BFT score was highly significantly correlated(P<0.001).The overall rate of false-positive and false-negative results was 4.0%.Conclusion: The BFT results measured in the three physical fitness test items were highly correlated with the output measured during the bicycle ergometer tests.The rate of false-positive and false-negative results was low.The test items thus represent an appropriate measurement instrument because the test items require few equipment and less time.Additionally,a large number of subjects can be assessed.We suggest that it would be more useful to assess the physical fitness of this special group exclusively on the basis of the BFT instead of using the bicycle ergometer test.展开更多
Purpose Thoroughbred racing jockeys compete at maximum physiological capacity in a sport with a high risk of falls and injury.A greater understanding of the physical capacities determining jockey performance may lead ...Purpose Thoroughbred racing jockeys compete at maximum physiological capacity in a sport with a high risk of falls and injury.A greater understanding of the physical capacities determining jockey performance may lead to minimum physical performance parameters and corrective interventions to improve jockey fitness and performance and reduce jockey and horse injury.The aim of this study was to develop appropriate physical testing procedures for jockeys and a physical fitness profile for different licence levels.Methods Fifty-eight jockeys(n=24 females,n=34 males),representing all apprentice jockeys licenced in New Zealand in 2021(100%,n=8 probationers and n=39 apprentices)and eleven professional jockeys(14%)were assessed to determine baseline physiological and fitness data.Descriptive statistics and boxplots were used to compare aerobic fitness,abdominal(core),upper and lower body strength,muscular power,reaction time,flexibility and a novel‘saddle’test targeting lower body strength,balance,and endurance between licencing levels.Effect Size(ES)was used to determine magnitude of dif-ferences between groups.Results More experienced jockeys had greater relative lower body strength(ES=0.2-0.7)and better balance(ES=0.5-0.9)compared to the less experienced groups.Jockeys who were in the top 20 of the premiership table(jockey rankings)had faster reaction times(ES=0.7)and greater core extensor strength(ES=0.7)than other cohorts.Most tests showed little dif-ferentiation between jockey licence levels,however the‘saddle test’showed greater variability in the less experienced race riders.This test may be an effective measure of jockey baseline performance.Conclusions These data could be used to inform minimum jockey licencing requirements and future physical fitness training programmes to increase jockey physiological fitness,thereby minimising risk of falls or injury due to physiological deficits and performance.展开更多
Hydrologic frequency analysis plays an important role in coastal and ocean engineering for structural design and disaster prevention in coastal areas. This paper proposes a Nonlinear Least Squares Method (NLSM), which...Hydrologic frequency analysis plays an important role in coastal and ocean engineering for structural design and disaster prevention in coastal areas. This paper proposes a Nonlinear Least Squares Method (NLSM), which estimates the three unknown parameters of the Weibull distribution simultaneously by an iteration method. Statistical test shows that the NLSM fits each data sample well. The effects of different parameter-fitting methods, distribution models, and threshold values are also discussed in the statistical analysis of storm set-down elevation. The best-fitting probability distribution is given and the corresponding return values are estimated for engineering design.展开更多
基金supported by the Program of Introducing Talents of Disciplines to Universities of the Ministry of Education and State Administration of the Foreign Experts Affairs of China (the 111 Project, Grant No.B08048)the Special Basic Research Fund for Methodology in Hydrology of the Ministry of Sciences and Technology of China (Grant No. 2011IM011000)
文摘The question of how to choose a copula model that best fits a given dataset is a predominant limitation of the copula approach, and the present study aims to investigate the techniques of goodness-of-fit tests for multi-dimensional copulas. A goodness-of-fit test based on Rosenblatt＇s transformation was mathematically expanded from two dimensions to three dimensions and procedures of a bootstrap version of the test were provided. Through stochastic copula simulation, an empirical application of historical drought data at the Lintong Gauge Station shows that the goodness-of-fit tests perform well, revealing that both trivariate Gaussian and Student t copulas are acceptable for modeling the dependence structures of the observed drought duration, severity, and peak. The goodness-of-fit tests for multi-dimensional copulas can provide further support and help a lot in the potential applications of a wider range of copulas to describe the associations of correlated hydrological variables. However, for the application of copulas with the number of dimensions larger than three, more complicated computational efforts as well as exploration and parameterization of corresponding copulas are required.
基金This work was supported in part by the National Natural Science Foundation of China(No.61901408)in part by Natural Science Foundation of Jiangsu Province(No.BK20170512)in part by Universities Natural Science Research Project of Jiangsu Province(No.17KJB413003).
文摘In cognitive radio networks,spectrum sensing under circumstances of dynamically varying noise and lacking prior information is a key challenge to the conventional spectrum sensing algorithms.Since the necessary information is rather difficult to obtain practically,most existing spectrum sensing methods are fettered in applications.Motivated by these,in this paper,a Frequency domain Goodness of Fit Test(FGoF)based spectrum sensing method is proposed.The FGoF makes full use of underlying information in Guard-Bands and the advantages of GoF test works for any distribution.Analytical and simulated results show that the FGoF is a robust spectrum sensing method in cognitive radio with the inherent advantages of invulnerability to dynamically varying noise.
文摘The logistic regression model has been become commonly used to study the association between a binary response variable;it is widespread application rests on its easy application and interpretation. The subject of assessment of goodness-of-fit in logistic regression model has attracted the attention of many scientists and researchers. Goodness-of-fit tests are methods to determine the suitability of the fitted model. Many of methods proposed and discussed for assessing goodness-of fit in logistic regression model, however, the asymptotic distribution of goodness-of-fit statistics are less examine, it is need more investigated. This work, will focus on assessing the behavior of asymptotic distribution of goodness-of-fit tests, also make comparison between global goodness-of-fit tests, and evaluate it by simulation.
基金supported by the Grant PID2020-120249RB-I00PID2023-148404OB-100funded by MCIN/AEI/10.13039/501100011033+4 种基金by the Andalusian Government(Junta de Andalucía,Plan Andaluz de Investigación,ref.P20_00124)by the Erasmus+Sport Programme of the European Union within the project FitBack4Literacy(No.101089829)Additional support is provided by the University of Granada,Plan Propio de Inves-tigación,Units of ExcellenceUnit of Excellence on Exercise,Nutrition and Health(UCEENS)by theCIBERobn Physiopa-thology of Obesity and Nutrition,and by the Spanish Network in Exercise and Health,EXERNET Network(RED2022-134800-Tand EXP_99828).
文摘Background:Physicalfitness in childhood and adolescence is associated with a variety of health outcomes and is a powerful marker of current and future health.However,inconsistencies in tests and protocols limit international monitoring and surveillance.The objective of the study was to seek international consensus on a proposed,evidence-informed,Youth Fitness International Test(YFIT)battery and protocols for health monitoring and surveillance in children and adolescents aged 618 years.Methods:We conducted an international modified Delphi study to evaluate the level of agreement with a proposed,evidence-based,YFIT of core health-relatedfitness tests and protocols to be used worldwide in 6-to 18-year-olds.This proposal was based on previous European and North American projects that systematically reviewed the existing evidence to identify the most valid,reliable,health-related,safe,and feasiblefitness tests to be used in children and adolescents aged 618 years.We designed a single-panel modified Delphi study and invited 216 experts from all around the world to answer this Delphi survey,of whom one-third are from low-to-middle income countries and one-third are women.Four experts were involved in the piloting of the survey and did not participate in the main Delphi study to avoid bias.We pre-defined an agreement of 80%among the expert participants to achieve consensus.Results:We obtained a high response rate(78%)with a total of 169fitness experts from 50 countries and territories,including 63 women and 61 experts from low-or middle-income countries/territories.Consensus(>85%agreement)was achieved for all proposed tests and protocols,supporting the YFIT battery,which includes weight and height(to compute body mass index as a proxy of body size/composition),the 20-m shuttle run(cardiorespiratoryfitness),handgrip strength,and standing long jump(muscularfitness).Conclusion:This study contributes to standardizingfitness tests and protocols used for research,monitoring,and surveillance across the world,which will allow for future data pooling and the development of international and regional sex-and age-specific reference values,health-related cut-points,and a global picture offitness among children and adolescents.
基金supported by Guangdong Basic and Applied Basic Research Foundation(Grant No.2022A1515011986)National Natural Science Foundation of China(Grant No.31700986).
文摘Regression estimates are biased when potential confounders are omitted or when there are other similar risks to validity.The instrumental variable(IV)method can be used instead to obtain less biased estimates or to strengthen causal inferences.One key assumption critical to the validity of the IV method is the exclusion assumption,which requires instruments to be correlated with the outcome variable only through endogenous predictors.The chi-square test of model fit is widely used as a diagnostic test for this assumption.Previous simulation studies assessed the power of this diagnostic test only in situations with strong violations of the exclusion assumption.However,low to moderate levels of assumption violation are not uncommon in reality,especially when the exclusion assumption is violated indirectly.In this study,we showed through Monte Carlo simulations that the chi-square model fit test suffered from a severe lack of power(<30%)to detect violations of the exclusion assumption when the level of violation was of typical size,and the IV causal inferences were severely inaccurate and misleading in this case.We thus advise using the IV method with caution unless there is a chance for thorough assumption diagnostics,like in meta-analyses or experiments.
基金Supported by National Natural Science Foundation of China (10775077, 10225522)
文摘A test statistic is proposed to perform the goodness-of-fit test in the unbinned maximum likelihood fit. Without using a detailed expression of the efficiency function, the test statistic is found to be strongly correlated with the maximum likelihood function if the efficiency function varies smoothly. We point out that the correlation coefficient can be estimated by the Monte Carlo technique. With the established method, two examples are given to illustrate the performance of the test statistic.
基金Supported by the National Natural Science Foundation of China(No.11471030,11471035,71201160)
文摘This study is undertaken to apply a bootstrap method of controlling the false discovery rate （FDR） when performing pairwise comparisons of normal means. Due to the dependency of test statistics in pairwise comparisons, many conventional multiple testing procedures can＇t be employed directly. Some modified pro- cedures that control FDR with dependent test statistics are too conservative. In the paper, by bootstrap and goodness-of-fit methods, we produce independent p-values for pairwise comparisons. Based on these indepen- dent p-values, plenty of procedures can be used, and two typical FDR controlling procedures are applied here. An example is provided to illustrate the proposed approach. Extensive simulations show the satisfactory FDR control and power performance of our approach. In addition, the proposed approach can be easily extended to more than two normal, or non-normal, balance or unbalance cases.
文摘<p> <span style="font-family:Verdana;">To address the drawbacks of the traditional Parker test in multivariate linear</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">models:</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">the process is cumbersome and computationally intensive,</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">we propose a new heteroscedasticity test.</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">A new heteroskedasticity test is proposed using the fitted values of the samples as new explanatory variables, reconstructing the regression model, and giving a new heteroskedasticity test based on the significance test of the coefficients, it is also compared with the existing Parker test which is improved using the principal component idea. Numerical simulations and empirical analyses show that the improved Parker test with the fitted values of the samples proposed in this paper is superior.</span> </p>
基金This project is supported by Beijing Natural Science Foundation by Chinese Natural ScienceFoundation.
文摘In this paper, a new statistics for testing two samples coming from the same population is derived from a simple linear model with an artificial parameter. Its limit distribution is a chi-squared distribution with 2 degrees of freedom under null hypothesis and the limit distribution is a noncentral chi-squared distribution with 2 degrees of freedom under certain sequence of alternative hypothesis. Finally, we make power comparison with other tests on two samples, especially, with Smirnov statistics.
文摘Background: Physical fitness tests are widely used to assess endurance,sprint ability,coordination and/or strength.The objective of the present study was to analyze the degree to which the results of the Bundeswehr Basis Fitness Test(BFT)–a physical fitness test comprising a sprint test(11×10-m shuttle test),a flexed-arm hang test and a 1000-m run–are consistent with the output measured during a bicycle ergometer test.The number of false-positive and falsenegative results with regard to the assessment of physical fitness were also examined.Methods: As part of a retrospective study,health assessments from 323 reenlistment examinations were evaluated regarding the output measured during a bicycle ergometer test and compared with the BFT results of the candidates.Results: Overall,a good correlation was shown between the bicycle ergometer test results and the results achieved in the BFT disciplines.All three disciplines of the BFT showed a highly significant correlation with the relative output achieved during the bicycle ergometer test(P<0.001),and also,the overall BFT score was highly significantly correlated(P<0.001).The overall rate of false-positive and false-negative results was 4.0%.Conclusion: The BFT results measured in the three physical fitness test items were highly correlated with the output measured during the bicycle ergometer tests.The rate of false-positive and false-negative results was low.The test items thus represent an appropriate measurement instrument because the test items require few equipment and less time.Additionally,a large number of subjects can be assessed.We suggest that it would be more useful to assess the physical fitness of this special group exclusively on the basis of the BFT instead of using the bicycle ergometer test.
基金funded by the New Zealand Equine Trust grant ET 2/2019.
文摘Purpose Thoroughbred racing jockeys compete at maximum physiological capacity in a sport with a high risk of falls and injury.A greater understanding of the physical capacities determining jockey performance may lead to minimum physical performance parameters and corrective interventions to improve jockey fitness and performance and reduce jockey and horse injury.The aim of this study was to develop appropriate physical testing procedures for jockeys and a physical fitness profile for different licence levels.Methods Fifty-eight jockeys(n=24 females,n=34 males),representing all apprentice jockeys licenced in New Zealand in 2021(100%,n=8 probationers and n=39 apprentices)and eleven professional jockeys(14%)were assessed to determine baseline physiological and fitness data.Descriptive statistics and boxplots were used to compare aerobic fitness,abdominal(core),upper and lower body strength,muscular power,reaction time,flexibility and a novel‘saddle’test targeting lower body strength,balance,and endurance between licencing levels.Effect Size(ES)was used to determine magnitude of dif-ferences between groups.Results More experienced jockeys had greater relative lower body strength(ES=0.2-0.7)and better balance(ES=0.5-0.9)compared to the less experienced groups.Jockeys who were in the top 20 of the premiership table(jockey rankings)had faster reaction times(ES=0.7)and greater core extensor strength(ES=0.7)than other cohorts.Most tests showed little dif-ferentiation between jockey licence levels,however the‘saddle test’showed greater variability in the less experienced race riders.This test may be an effective measure of jockey baseline performance.Conclusions These data could be used to inform minimum jockey licencing requirements and future physical fitness training programmes to increase jockey physiological fitness,thereby minimising risk of falls or injury due to physiological deficits and performance.
基金supported by the 10th Five-Year Plan Key Project of China and the National Science Foundation of China(grant No.40076028).
文摘Hydrologic frequency analysis plays an important role in coastal and ocean engineering for structural design and disaster prevention in coastal areas. This paper proposes a Nonlinear Least Squares Method (NLSM), which estimates the three unknown parameters of the Weibull distribution simultaneously by an iteration method. Statistical test shows that the NLSM fits each data sample well. The effects of different parameter-fitting methods, distribution models, and threshold values are also discussed in the statistical analysis of storm set-down elevation. The best-fitting probability distribution is given and the corresponding return values are estimated for engineering design.
