Quantile Regression Varying-Coefficient Model in The Case of Longitudinal Data: A Study on The Success Rates of Secondary Schools in Al-Diwaniyah Governorate \ Iraq. (2025). Al Kut Journal of Economics and Administrative Sciences, 17(56), 1097-1111. https://kjeas.uowasit.edu.iq/index.php/kjeas/article/view/1393