We use the form=a+bx

for the least-squares line. In some computer printouts, the least-squares equation is not given directly. Instead, the value of the constantais given, and the coefficientbof the explanatory or predictor variable is displayed. Sometimesais referred to as the constant, and sometimes as the intercept. Data from a report showed the following relationship between elevation (in thousands of feet) and average number of frost-free days per year in a state.

A Minitab printout provides the following information.

PredictorCoefSE CoefTPConstant316.8928.3111.240.002Elevation-31.9473.511-8.790.003S = 11.8603R-Sq =94.8%Notice that "Elevation" is listed under "Predictor." This means that elevation is the explanatory variablex. Its coefficient is the slopeb. "Constant" refers toain the equation=a+bx.

(a) Use the printout to write the least-squares equation.=

+

x

(b) For each 1000-foot increase in elevation, how many fewer frost-free days are predicted? (Round your answer to three decimal places.)

(c) The printout gives the value of the coefficient of determinationr². What is the value ofr? Be sure to give the correct sign forrbased on the sign ofb. (Round your answer to four decimal places.)

(d) What percentage of the variation inycan be explained by the corresponding variation inxand the least-squares line?

%

What percentage is unexplained?

%