arXiv subjects

Sévérien Nkurunziza

Publications and source records attributed to Sévérien Nkurunziza.

4 recordsLinked to original sources

arXiv2017

On the joint asymptotic distribution of the restricted estimators in multivariate regression model

The main Theorem of Jain et al.[Jain, K., Singh, S., and Sharma, S. (2011), Re- stricted estimation in multivariate measurement error regression model; JMVA, 102, 2, 264-280] is established in its full generality. Namely, we derive the joint asymp- totic normality of the unrestricted estimator (UE) and the restricted estimators of the matrix of the regression coefficients. The derived result holds under the hypothesized restriction as well as under the sequence of alternative restrictions. In addition, we establish Asymptotic Distributional Risk for the estimators and compare their relative performance. It is established that near the restriction, the restricted estimators (REs) perform better than the UE. But the REs perform worse than the unrestricted estimator when one moves far away from the restriction.

math.ST↗

arXiv2017

On convergence of the sample correlation matrices in high-dimensional data

In this paper, we consider an estimation problem concerning the matrix of correlation coefficients in context of high dimensional data settings. In particular, we revisit some results in Li and Rolsalsky [Li, D. and Rolsalsky, A. (2006). Some strong limit theorems for the largest entries of sample correlation matrices, The Annals of Applied Probability, 16, 1, 423-447]. Four of the main theorems of Li and Rolsalsky (2006) are established in their full generalities and we simplify substantially some proofs of the quoted paper. Further, we generalize a theorem which is useful in deriving the existence of the pth moment as well as in studying the convergence rates in law of large numbers.

math.ST↗

arXiv2015

Optimal method in multiple regression with structural changes

In this paper, we consider an estimation problem of the regression coefficients in multiple regression models with several unknown change-points. Under some realistic assumptions, we propose a class of estimators which includes as a special cases shrinkage estimators (SEs) as well as the unrestricted estimator (UE) and the restricted estimator (RE). We also derive a more general condition for the SEs to dominate the UE. To this end, we generalize some identities for the evaluation of the bias and risk functions of shrinkage-type estimators. As illustrative example, our method is applied to the "gross domestic product" data set of 10 countries whose USA, Canada, UK, France and Germany. The simulation results corroborate our theoretical findings.

math.ST↗

arXiv2014

A short note on model selection by LASSO methods in a change-point model

In Ciuperca (2012) (Ciuperca. Model selection by LASSO methods in a change-point model, Stat. Papers, 2012; (in press)), the author considered a linear regression model with multiple change-points occurring at unknown times. In particular, the author studied the asymptotic properties of the LASSO-type and of the adaptive LASSO estimators. While the established results seem interesting, we point out some major errors in proof of the most important result of the quoted paper. Further, we present a corrected result and proof.

stat.ME↗