( iv ) The goodness of fit is always satisfactory ( χ 2 /d.o.f . < 3 ) at weak and intermediate couplings ( u ∈ [ 0.8873 , 1.8811 ] ) . In a limited number of cases at stronger couplings the value tends to rise considerably , but this apparently does not depend systematically on the number of fitted points and choice of fitting Ansatz . In any case , given the small number of fitted data points , χ 2 /d.o.f . is a goodness - of - fit criterion of relatively limited value . Instead , the total χ 2 /d.o.f . varies between 1 and 2 , indicating satisfactory overall quality of the fits .