Modified quadratic loss function for a trivariate response with the exact feasible region for parameters

► This paper deals with quadratic quality loss function for trivariate response. ► We presented modification of Taguchi's quadratic quality loss function (QQLF). ► We solved analytically nonlinear constraint for coefficients kij, i ≠ j of QQLF. ► We found out exact feasible region for coefficients kij, i ≠ j of QQLF.