An aircraft company wanted to predict the number of worker-hours necessary to finish the design of a new plane. Relevant explanatory variables were thought to be the plane’s top speed, its weight, and the number of parts it had in common with other models built by the company. A sample of 27 of the company’s planes was taken, and the following model was estimated:
y` = β0 + β1x1i + β2x2i + β3x3i + εi
where
yi = design effort, in millions of worker-hours
x1i = plane’s top speed, in miles per hour
x2i = plane’s weight, in tons
x3i = percentage number of parts in common with other models
The estimated regression coefficients were as follows:
b0 = 2 b1 = 0.661 b2 = 0.065 b3 = -0.018
Interpret these estimates.