Using data on the characteristics of houses that sold recently in a city of interest, you would like to specify the way in which features such as the size (in square feet) and number of bedrooms relate to the sale price. You are working out an equation that asserts that the sales price is given by a formula that involves the house’s characteristics and parameters (such as the dollar value of an additional bedroom) that are estimated from the data. What main activity of statistics are you involved with?