The article “Bank Full Discharge of Rivers” (Water Resources Journal [1978]: 1141– 1154)...

The article “Bank Full Discharge of Rivers” (Water Resources Journal [1978]: 1141– 1154) reported data on y discharge amount (m²/s), x₁ = flow area (m²), and x² = slope of the water surface (m/m) obtained at n = 10 floodplain stations. A multiple regression model using x₁, x₂, and x₃ = x₁x₂ was fit to these data, and partial Minitab output appears here.

a. Perform the model utility test using a significance level of .05.

b. Is the interaction term important? Test using a .05 significance level.

c. Does it bother you that the model utility test indicates a useful model, but all values in the t-ratio column of the output are small? Explain.