The article ??Approach to Confidence Interval Estimation for Curve Numbers?? (R. McCuen, Journal of Hydrologic Engineering, 2002:43??48) discusses the relationship between rainfall depth and runoff depth at several locations. At one particular location, rainfall depth and runoff depth were recorded for 13 rainstorms. Following is MINITAB output for a fit of the least-squares line to predict runoff depth from rainfall depth (both measured in inches).

a. Predict the runoff for a storm with 2.5 in. of rainfall.

b. Someone claims that if two storms differ in their rainfall by 1 in., then their runoffs will differ, on the average, by 1 in. as well. Is this a plausible claim? Explain.

c. It is a fact that if the rainfall is 0, the runoff is 0. Is the least-squares line consistent with this fact? Explain.

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The regression equation is Runoff = -0.23 + 0.73 Rainfall Predictor Constant Rainfall Coef -0.23429 0.72868 SE Coef 0.23996 0.06353 T -0.98 P 0.350 0.000 11.47 S = 0.40229 R-Sq 92.3% R-Sq(adj) = 91.6% Analysis of Variance Source DF 1 11 12 SS 21.290 1.780 23.070 MS 21.290 0.16184 F P 131.55 Regression Residual Error Total 0.000