Journal of the Iranian Statistical Society

Journal of the Iranian Statistical Society

Comparison of Standardized and Adjusted Working Residuals for Gamma-Pareto Regression and Gamma-Pareto Ridge Regression Models

Document Type : Original Article

Authors
Department of Statistics, Bahauddin Zakariya University (BZU), Multan, Pakistan,60800
10.22034/jirss.2026.2083523.1177
Abstract
Influential observations can substantially affect the estimation, interpretation, and predictive performance of Gamma-Pareto regression models, particularly when multicollinearity is present. This study investigates the detection of influential observations in the Gamma-Pareto regression model and its ridge-based counterpart, the Gamma-Pareto ridge regression model. Several established diagnostic measures, including the Covariance Ratio, Welch Distance, and Hadi’s Measure, together with their ridge-regression counterparts, are considered for assessing the influence of individual observations. To enhance the reliability of influence diagnostics in the presence of dispersion-related effects, we used an extended Hadi’s Measure for the Gamma-Pareto ridge regression model based on standardized and adjusted working residuals. The diagnostic measures are evaluated through comprehensive analyses of both real and simulated datasets under varying levels of dispersion. The results demonstrate that the proposed Hadi’s Measure in Ridge provides a more effective and stable mechanism for identifying influential observations than the conventional diagnostics, with different dispersion settings. These findings highlight the usefulness of incorporating standardized and adjusted working residuals into influence diagnostics and provide a practical framework for detecting influential observations in Gamma-Pareto ridge regression model.
Keywords
Subjects

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Articles in Press, Accepted Manuscript
Available Online from 12 November 2026

  • Receive Date 08 January 2026
  • Revise Date 28 September 2026
  • Accept Date 01 October 2026