Response surface methodology: Asymptotic normality of the optimal   solution
  Sensitivity analysis of the optimal solution in response surface methodology is studied and an explicit form of the effect of perturbation of the regression coefficients on the optimal solution is obtained. The characterisation of the critical point of the convex program corresponding to the optimum of a response surface model is also studied. The asymptotic normality of the optimal solution follows by standard methods. 
Jose A. Diaz-Garcia, Jose E. Rodriguez and Rogelio Ramos-Quiroga
math.ST stat.TH