Analysis of parameters

The coefficients of a regression model are estimates of unknown parameters.
These are population parameters that characterize the "true" or population
regression line.

The estimates of these parameters provide a numeric value (sample estimates)
that can be used to answer questions like the following:

(1) How much does the quantity demanded of a certain product change as a
result of a price change?

(2) What is the marginal effect on average housing prices of an increase in
total square footage?

(3) What is the expected change in sales as a result of a 10% increase in the
advertising expenditure budget?