Understanding regression
Regression is concerned with specifying the relationship between a single numeric dependent variable (the value to be predicted) and one or more numeric independent variables (the predictors). We'll begin by assuming that the relationship between the independent and dependent variables follows a straight line.
Tip
The origin of the term "regression" to describe the process of fitting lines to data is rooted in a study of genetics by Sir Francis Galton in the late 19th century. Galton discovered that fathers that were extremely short or extremely tall tended to have sons whose heights were closer to average. He called this phenomenon "regression to the mean".
You might recall from algebra that lines can be defined in a slope-intercept form similar to y = a + bx, where y is the dependent variable and x is the independent variable. In this formula, the slope b indicates how much the line rises for each increase in x. The variable a indicates the value of y when x = 0...