Question

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

Monthly Natural Gas Consumption (cubic feet) y	Thickness of Insulation (inches) X1	Outdoor Temperature (˚F) X2
30.3	6	40
26.9	12	40
22.1	8	49

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

Ŷ = 62.65 – 1.86X1 – 0.52X2

1. How much of the natural gas can homeowners expect to use per month if they install 6 inches of insulation and the outdoor temperature is 40 ˚F?
2. What effect would installing 7 inches of insulation instead of 6 have on th monthly natural gas consumption (assuming the outdoor temperature remains at 40 ˚F)?
3. Why are the regression coefficients X1 & X2 negative? Is this logical?

Answer 1

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