I was trying to do a 5 factor 4 level experiment and according to the MiniTab software it was suggested L16 array of experiments. Now if I try to the experiment the degree of freedom for L16 expt is 15 as well as the total degree of freedom is 5x(4-1)=15. Hence, there is no residual error and I can not perform the ANNOVA. Please suggest what should I do. Please help this is urgent.