Question

Cellulon, a manufacturer of home insulation, wants to develop guidelines for builders and consumers on how the thickness of the insulation in the attic of a home and the outdoor temperature affect natural gas consumption. In the laboratory, it varied the insulation thickness and temperature. A few of the findings are:

Monthly Natural Gas Consumption (cubic feet),		Thickness of Insulation (inches),		Outdoor Temperature (ºF),
y		x1		x2
30.3		6.0		40.0
24.2		12		40
27.9		8		49

On the basis of the sample results, the regression equation is:

yˆ y⁢^⁢  = 56.26 − 0.66x₁ − 0.59x₂

1. How much natural gas can homeowners expect to use per month if they install 6 inches of insulation and the outdoor temperature is 40 degrees F? (Round your answer to 2 decimal places.)

2. What effect would installing 7 inches of insulation instead of 6 have on the monthly natural gas consumption (assuming the outdoor temperature remains at 40 degrees F)? (Round your answers to 2 decimal places.)

3. The regression coefficients b₁ and b₂ are negative? Is this logical?

Answer 1