An extension of the D2 test statistic to test the equality of mean for high-dimensional and k-th ... more An extension of the D2 test statistic to test the equality of mean for high-dimensional and k-th order array-variate data using k-self similar compound symmetry (k-SSCS) covariance structure is derived. The k-th order data appear in many scientific fields including agriculture, medical, environmental and engineering applications. We discuss the property of this k-SSCS covariance structure, namely, the property of Jordan algebra. We formally show that our D2 test statistic for k-th order data is an extension or the generalization of the D2 test statistic for second-order data and for third-order data, respectively. We also derive the D2 test statistic for third-order data and illustrate its application using a medical dataset from a clinical trial study of the eye disease glaucoma. The new test statistic is very efficient for high-dimensional data where the estimation of unstructured variance-covariance matrix is not feasible due to small sample size.
Statement: We propose an extension of the Birnbaum-Saunders distribution to model the more realis... more Statement: We propose an extension of the Birnbaum-Saunders distribution to model the more realistic situations where the fatigue failure time of a material is due to the growth of multiple cracks. The properties of the extended Birnbaum-Saunders (EBS) distribution are provided and its purpose to model the fatigue failure time of a material due to the growth of equicorrelated multiple cracks is proposed. Discussion: The moment estimates (MEs) and the maximum likelihood estimates (MLEs) of the unknown parameters of the EBS distribution based on independent but not identically distributed (i.n.i.d.) random variables are obtained. Monte Carlo (MC) simulations are done to assess the performance of the parameter estimators of the EBS distribution with different number of cracks for different samples. Summary: Comparisons of the parameter estimates and their standard deviations are made between this new EBS distribution with i.n.i.d. samples and the EBS distribution with i.i.d. samples. C...
Corporate reputation (CR) has become a fashionable topic due, among other reasons, to the recent ... more Corporate reputation (CR) has become a fashionable topic due, among other reasons, to the recent financial and economic crisis and spreading corporate scandals. Given its interdisciplinary character and intangible nature, CR has been a frequent issue in many disciplines, but scarcely present in the business ethics field. This neglect is odd since a good reputation is one of the most valuable consequences of doing the right things and the things right. In this paper, we intend to explain this absence through three hypotheses: a) business ethics literature largely identifies corporate reputation and corporate social responsibility; b) corporate reputation overlaps with corporate image and corporate identity, resulting interchangeable constructs; and c) business ethics scholars have focused on the negative side of the reputation phenomenon, highlighting reputational risk more than benefits. Based on a bibliometric analysis of the top journal of business ethics literature over a recent decade (2002-2011), we finally confirmed the three hypotheses although c) only partially. In addition, the findings of this study will allow for a deeper understanding of the link between looking good and doing well.
Communications in Statistics - Theory and Methods, 2014
Abstract Although devised in 1936 by Fisher, discriminant analysis is still rapidly evolving, as ... more Abstract Although devised in 1936 by Fisher, discriminant analysis is still rapidly evolving, as the complexity of contemporary data sets grows exponentially. Our classification rules explore these complexities by modeling various correlations in higher-order data. ...
An endemic of chronic kidney disease (CKD) of unknown cause among rural inhabitants in Central Am... more An endemic of chronic kidney disease (CKD) of unknown cause among rural inhabitants in Central America has been identified. Young and otherwise healthy men working in plantations are frequently affected. The name Mesoamerican nephropathy (MeN) has been suggested. Clinically, MeN presents with low-grade proteinuria and progressive kidney failure. The renal pathology of this disease has not yet been described. Case series. 8 male patients with CKD of unknown cause and clinically suspected MeN were recruited from a nephrology unit in El Salvador. All recruited patients had been working on plantations. Kidney biopsies, blood, and urine samples were collected. Renal morphology examined with light microscopy, immunofluorescence, and electron microscopy; clinical and biochemical characteristics. A similar pattern was seen in all 8 biopsy specimens, with extensive glomerulosclerosis (29%-78%) and signs of chronic glomerular ischemia in combination with tubular atrophy and interstitial fibrosis, but only mild vascular lesions. Electron microscopy indicates podocytic injury. Biochemical workup showed reduced estimated glomerular filtration rate (27-79 mL/min/1.73 m(2) with the CKD Epidemiology Collaboration [CKD-EPI] creatinine equation), low-grade albuminuria, and increased levels of tubular injury biomarkers. Hypokalemia was found in 6 of 8 patients. Small number of patients from one country. This study is the first report of the biochemical and morphologic findings in patients with MeN. Our findings indicate that MeN constitutes a previously unrecognized kidney disease with damage to both glomerular and tubulointerstitial compartments.
Communications in Statistics-theory and Methods, 2010
This article proposes a quadratic extension of the traditional classification rules for multiple ... more This article proposes a quadratic extension of the traditional classification rules for multiple classes based on equicorrelated training vectors by using multivariate equicorrelation. This new classification rule can incorporate within sample dependencies, thus appropriate for non random samples.
An extension of the D2 test statistic to test the equality of mean for high-dimensional and k-th ... more An extension of the D2 test statistic to test the equality of mean for high-dimensional and k-th order array-variate data using k-self similar compound symmetry (k-SSCS) covariance structure is derived. The k-th order data appear in many scientific fields including agriculture, medical, environmental and engineering applications. We discuss the property of this k-SSCS covariance structure, namely, the property of Jordan algebra. We formally show that our D2 test statistic for k-th order data is an extension or the generalization of the D2 test statistic for second-order data and for third-order data, respectively. We also derive the D2 test statistic for third-order data and illustrate its application using a medical dataset from a clinical trial study of the eye disease glaucoma. The new test statistic is very efficient for high-dimensional data where the estimation of unstructured variance-covariance matrix is not feasible due to small sample size.
Statement: We propose an extension of the Birnbaum-Saunders distribution to model the more realis... more Statement: We propose an extension of the Birnbaum-Saunders distribution to model the more realistic situations where the fatigue failure time of a material is due to the growth of multiple cracks. The properties of the extended Birnbaum-Saunders (EBS) distribution are provided and its purpose to model the fatigue failure time of a material due to the growth of equicorrelated multiple cracks is proposed. Discussion: The moment estimates (MEs) and the maximum likelihood estimates (MLEs) of the unknown parameters of the EBS distribution based on independent but not identically distributed (i.n.i.d.) random variables are obtained. Monte Carlo (MC) simulations are done to assess the performance of the parameter estimators of the EBS distribution with different number of cracks for different samples. Summary: Comparisons of the parameter estimates and their standard deviations are made between this new EBS distribution with i.n.i.d. samples and the EBS distribution with i.i.d. samples. C...
Corporate reputation (CR) has become a fashionable topic due, among other reasons, to the recent ... more Corporate reputation (CR) has become a fashionable topic due, among other reasons, to the recent financial and economic crisis and spreading corporate scandals. Given its interdisciplinary character and intangible nature, CR has been a frequent issue in many disciplines, but scarcely present in the business ethics field. This neglect is odd since a good reputation is one of the most valuable consequences of doing the right things and the things right. In this paper, we intend to explain this absence through three hypotheses: a) business ethics literature largely identifies corporate reputation and corporate social responsibility; b) corporate reputation overlaps with corporate image and corporate identity, resulting interchangeable constructs; and c) business ethics scholars have focused on the negative side of the reputation phenomenon, highlighting reputational risk more than benefits. Based on a bibliometric analysis of the top journal of business ethics literature over a recent decade (2002-2011), we finally confirmed the three hypotheses although c) only partially. In addition, the findings of this study will allow for a deeper understanding of the link between looking good and doing well.
Communications in Statistics - Theory and Methods, 2014
Abstract Although devised in 1936 by Fisher, discriminant analysis is still rapidly evolving, as ... more Abstract Although devised in 1936 by Fisher, discriminant analysis is still rapidly evolving, as the complexity of contemporary data sets grows exponentially. Our classification rules explore these complexities by modeling various correlations in higher-order data. ...
An endemic of chronic kidney disease (CKD) of unknown cause among rural inhabitants in Central Am... more An endemic of chronic kidney disease (CKD) of unknown cause among rural inhabitants in Central America has been identified. Young and otherwise healthy men working in plantations are frequently affected. The name Mesoamerican nephropathy (MeN) has been suggested. Clinically, MeN presents with low-grade proteinuria and progressive kidney failure. The renal pathology of this disease has not yet been described. Case series. 8 male patients with CKD of unknown cause and clinically suspected MeN were recruited from a nephrology unit in El Salvador. All recruited patients had been working on plantations. Kidney biopsies, blood, and urine samples were collected. Renal morphology examined with light microscopy, immunofluorescence, and electron microscopy; clinical and biochemical characteristics. A similar pattern was seen in all 8 biopsy specimens, with extensive glomerulosclerosis (29%-78%) and signs of chronic glomerular ischemia in combination with tubular atrophy and interstitial fibrosis, but only mild vascular lesions. Electron microscopy indicates podocytic injury. Biochemical workup showed reduced estimated glomerular filtration rate (27-79 mL/min/1.73 m(2) with the CKD Epidemiology Collaboration [CKD-EPI] creatinine equation), low-grade albuminuria, and increased levels of tubular injury biomarkers. Hypokalemia was found in 6 of 8 patients. Small number of patients from one country. This study is the first report of the biochemical and morphologic findings in patients with MeN. Our findings indicate that MeN constitutes a previously unrecognized kidney disease with damage to both glomerular and tubulointerstitial compartments.
Communications in Statistics-theory and Methods, 2010
This article proposes a quadratic extension of the traditional classification rules for multiple ... more This article proposes a quadratic extension of the traditional classification rules for multiple classes based on equicorrelated training vectors by using multivariate equicorrelation. This new classification rule can incorporate within sample dependencies, thus appropriate for non random samples.
Uploads
Papers by Ricardo D Leiva