Main Article Content

Abstract

Rank-based analysis of linear models is based on selecting an appropriate score function. The information about the shape of the underlying distribution is necessary for the optimal selection; leading towards asymptotically efficient analysis. In this study, we analyzed the multilevel model with cluster-correlated error terms following a family of skew-t distribution with the rank-based approach based on score function derived for the class of skew-normal distribution. The rank fit is compared with the Restricted Maximum Likelihood (REML) estimation in terms of validity and efficiency for different sample sizes. A Monte Carlo simulation study is carried out over skewed-t and contaminated-t distribution with a range of skewness parameters from moderately to highly skewed. The standard error of regression coefficients is significantly reduced in the rank-based approach and further reduces for a large sample size. Rank-based fit appeared asymptotically efficient than REML for each shape parameter of skewness in skew-t and contaminated-t distribution computed through a calculation of precision. The empirical validity of fixed effects is obtained up to the nominal level 0.95 in REML but not rank-based with skew-normal score function.

Keywords

Multilevel models Rank-based REML Skew-normal Skew-t

Article Details

How to Cite
Saleem, S., & Sherwani, R. A. K. (2021). Efficient Rank-Based Analysis of Multilevel Models for the Family of Skew-t Errors. Pakistan Journal of Statistics and Operation Research, 17(1), 89-98. https://doi.org/10.18187/pjsor.v17i1.3339

References

  1. Al-shomrani, A. A. (2003). A Comparison of Different Schemes for Selecting and Estimating Score Functions Based on Residuals [Western Michigan University].
  2. Arellano-Valle, R. B., & Azzalini, A. (2013). The centred parameterization and related quantities of the skew-t distribution. Journal of Multivariate Analysis, 113, 73-90.
  3. Auda, H. A., McKean, J. W., Kloke, J. D., & Sadek, M. (2017). A Monte Carlo study of REML and robust rank-based analyses for the random intercept mixed model. Communications in Statistics: Simulation and Computation, 48(3), 837-860.
  4. Azzalini, A. (1985). A Class of Distributions Which Includes the Normal Ones. Scandinavian Journal of Statistics, 12(2), 171-178.
  5. Azzalini, A, & Capitanio, A. (2014). The Skew-Normal and Related Families. Cambridge University Press.
  6. Azzalini, Adelchi. (2013). The skew-normal and related families. Cambridge University Press.
  7. Azzalini, Adelchi. (2014). The R sn Package: The skew-normal and skew-t distributions (1.0-0).
  8. Azzalini, Adelchi, & Capitanio, A. (2003). Distributions generated by perturbation of symmetry with emphasis on a multivariate skew tâ€distribution. Journal of the Royal Statistical Society: Series B (Statistical Methodology), 65(2), 367-389.
  9. Azzalini, Adelchi, & Genton, M. G. (2008). Robust likelihood methods based on the skewâ€t and related distributions. International Statistical Review, 76(1), 106-129.
  10. Basalamah, D. (2017). Statistical Inference for a New Class of Skew t Distribution and Its Related Properties. Bowling Green State University.
  11. Goldstein, H. (1995). Multilevel statistical models (second edi). Edward Arnold.
  12. Hájek, J., & Sidák, Z. (1967). Theory of rank tests. Academic Press.
  13. Hettmansperger, T. P., & McKean, J. W. (2010). Robust nonparametric statistical methods (second). CRC Press.
  14. Jaeckel, L. A. (1972). Estimating Regression Coefficients by Minimizing the Dispersion of the Residuals. The Annals of Mathematical Statistics, 43(5), 1449-1458.
  15. Kloke, J. D., & McKean, J. W. (2012). Rfit: Rank-based estimation for linear models. The R Journal, 4(2), 57-64.
  16. Kloke, John D., & Mckean, J. W. (2014). Nonparametric Statistical Methods Using R. Chapman and Hall/CRC.
  17. Kloke, John D, McKean, J. W., & Rashid, M. M. (2009). Rank-Based Estimation and Associated Inferences for Linear Models With Cluster Correlated Errors. Journal of the American Statistical Association, 104(485), 384-390.
  18. McKean, J. W., & Kloke, J. D. (2014). Efficient and adaptive rank-based fits for linear models with skew-normal errors. Journal of Statistical Distributions and Applications, 1(1), 1-18.