The objective of this research is to compare multiple regression coefficients estimating methods with existence of multicollinearity among independent variables. The estimation methods are Ordinary Least Squares method (OLS). Restricted Least Squares method (RLS). Restricted Ridge Regression method (RRR) and Restricted Liu method (RL) when restrictions are true and restrictions are no... https://parisnaturalfoodes.shop/product-category/org-spruce-black-essential-oil/