Stochastic analysis of covariance when the error distribution is long-tailed symmetric

ABSTRACT

In this study, we consider stochastic one-way analysis of covariance model when the distribution of the error terms is long-tailed symmetric. Estimators of the unknown model parameters are obtained by using the maximum likelihood (ML) methodology. Iteratively reweighting algorithm is used to compute the ML estimates of the parameters. We also propose new test statistic based on ML estimators for testing the linear contrasts of the treatment effects. In the simulation study, we compare the efficiencies of the traditional least-squares (LS) estimators of the model parameters with the corresponding ML estimators. We also compare the power of the test statistics based on LS and ML estimators, respectively. A real-life example is given at the end of the study.

KEYWORDS:

• ANCOVA
• stochastic covariate
• long-tailed symmetric
• robustness
• iteratively reweighting algorithm

Disclosure statement

No potential conflict of interest was reported by the authors.