An automotive engineer computed a least-squares regression line for predicting the gas mileage (miles per gallon, or mpg) of a certain vehicle from its speed in mph. The results are presented in The following Excel output.

$\begin{array} { l | c }
& \text { Coefficients } \
\hline \text { Intercept } & 38.5176991 \
\hline \text { Speed } & - 0.19495575
\end{array}$

Predict the gas mileage when the vehicle is traveling at 56 mph.
A) 25.2 mpg
B) 49 mpg
C) 28 mpg
D) 31 mpg

Question

An automotive engineer computed a least-squares regression line for predicting the gas mileage (miles per gallon, or mpg) of a certain vehicle from its speed in mph. The results are presented in The following Excel output.

$\begin{array} { l | c } 
& \text { Coefficients } \
\hline \text { Intercept } & 38.5176991 \
\hline \text { Speed } & - 0.19495575
\end{array}$

Predict the gas mileage when the vehicle is traveling at 56 mph.
A) 25.2 mpg
B) 49  mpg
C) 28 mpg
D) 31 mpg

Quizplus · Accepted Answer

The regression equation is:
mpg = 38.5176991 - 0.19495575(speed)

To predict the gas mileage at 56 mph, we substitute speed = 56 into the equation:
mpg = 38.5176991 - 0.19495575(56)
mpg = 38.5176991 - 10.927439
mpg = 27.59026

Rounding to one decimal place, the predicted gas mileage is 27.6 mpg, which corresponds to choice C.