MODIFIED FUZZY-ROBUST RIDGE REGRESSION FOR MULTICOLLINEAR, OUTLIER-CONTAMINATED DATA
Abstract
Multicollinearity is known to have a significant impact on the stability of linear regression parameter estimation, while the presence of outliers tends to compound this problem. Ridge regression helps to improve the multicollinearity problem, but it is highly sensitive to outliers. This paper proposes Modified Fuzzy Robust Ridge Regression (MFRRR), which modifies classical ridge regression by adapting the penalty parameter through modified fuzzy robust estimators based on weighted residual membership functions. The method is evaluated under challenging data conditions involving simultaneous multicollinearity, outliers, and fuzzy uncertainty. Performance is assessed using both a real body fat dataset and Monte Carlo simulations with varying sample sizes correlation levels and contamination rates . MFRRR is compared to ordinary least squares (OLS), ridge regression, and robust ridge regression based on the mean absolute error (MAE) as an evaluation criterion. These findings indicate that MFRRR is always associated with smaller prediction errors and more reliable parameter estimates, especially when there is high multicollinearity and data contamination
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References
Akbari, M. G., & Hesamian, G. (2019). A partial-robust-ridge-based regression model with fuzzy predictors-responses. Journal of Computational and Applied Mathematics, 351, 290–301. https://doi.org/10.1016/j.cam.2018.11.006
Bas, E., & Egrioglu, E. (2024). Robust picture fuzzy regression functions approach based on M-estimators for the forecasting problem. Computational Economics, 65(3), 2775–2810. https://doi.org/10.1007/s10614-024-10647-9
Belsley, D. A. (1991). Conditioning diagnostics: Collinearity and weak data in regression. Wiley-Interscience.
Choi, S., Jung, H.-Y., & Kim, H. (2019). Ridge fuzzy regression model. International Journal of Fuzzy Systems, 21. https://doi.org/10.1007/s40815-019-00692-0
Farnoosh, R., Ghasemian, J., & Solaymani Fard, O. (2020). Integrating ridge-type regularization in fuzzy nonlinear regression. Computational and Applied Mathematics, 39(2), 1–17. https://doi.org/10.1590/S1807-03022012000200006
Hesamian, G., & Akbari, M. G. (2020). A robust varying coefficient approach to fuzzy multiple regression model. Journal of Computational and Applied Mathematics, 371, 112704. https://doi.org/10.1016/j.cam.2019.112704
Hoerl, A. E., & Kennard, R. W. (1970). Ridge regression: Biased estimation for nonorthogonal problems. Technometrics, 12(1), 55–67. https://doi.org/10.1080/00401706.1970.10488634
Hong, D. H., & Hwang, C. (2004). Ridge regression procedures for fuzzy models using triangular fuzzy numbers. International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems, 12, 145–159. https://doi.org/10.1142/S0218488504002746
Hong, D. H., Hwang, C., & Ahn, C. (2004). Ridge estimation for regression models with crisp inputs and Gaussian fuzzy output. Fuzzy Sets and Systems, 142, 307–319. https://doi.org/10.1016/S0165-0114(03)00002-2
Ismaeel, S. S., Midi, H., & Omar, K. M. T. (2024). A remedial measure of multicollinearity in multiple linear regression in the presence of high leverage points. Sains Malaysiana, 53(4), 907–920. https://doi.org/10.17576/jsm-2024-5304-14
Karbasi, D., Nazemi, A., & Rabiei, M. R. (2021). An optimization technique for solving a class of ridge fuzzy regression problems. Neural Processing Letters, 53, 3307–3338. https://doi.org/10.1007/s11063-021-10538-2
Kareem, R. E., & Mohammed, M. J. (2023). Fuzzy bridge regression model estimating via simulation. Journal of Economics and Administrative Sciences, 29(136), 60–69. https://doi.org/10.33095/jeas.v29i136.2607
Kim, H., & Jung, H.-Y. (2020). Ridge fuzzy regression modelling for solving multicollinearity. Mathematics, 8(9), 1572. https://doi.org/10.3390/math8091572
Penrose, K. W., Nelson, A., & Fisher, A. (1985). Generalized body composition prediction equation for men using simple measurement techniques. Medicine & Science in Sports & Exercise, 17(2), 189. https://journals.lww.com/00005768-198504000-00037
Rabiei, M., Arashi, M., & Farrokhi, M. (2019). Fuzzy ridge regression with fuzzy input and output. Soft Computing, 23, 4164. https://doi.org/10.1007/s00500-019-04164-3
Salih, V. M., & Ismaeel, S. (2025). Enhancing Parameter Estimation for Fuzzy Robust Regression in the Presence of Outliers. Statistics, Optimization & Information Computing, 14(4), 1795-1812. https://doi.org/10.19139/soic-2310-5070-2656
Tsai, T. R., & Wu, S. J. (2002). Fuzzy-weighted estimation in ridge regression analysis. Journal of Information and Optimization Sciences, 23(2), 259–271. https://doi.org/10.1080/02522667.2002.10698995
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Copyright (c) 2026 Vaman M. Salih, and Shelan S. Ismaeel

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