highly significantP < 0.0001
There were no significant effects of dropping the “treatment” × “stage” interaction ( χ 2 = 0.62, Δdf = 3, P = 0.89) nor of dropping “stage” ( χ 2 = 2.23, Δdf = 1, P = 0.14) but again dropping “treatment” had a highly significant effect upon model fit ( χ 2 = 48.52, Δdf = 3, P < 0.0001; Table 3 , experiment 2).