In many cases, when we are interested in forecasting or predicting the value of a variable (dependent variable) given the value of a second variable (independent variable), we need to know exactly how the variables are related. Regression analysis allows us to estimate the structure of this relationship with a certain degree of confidence.

The use of simple linear regression analysis requires the relationship between the two variable to be linear, and the direction of causation to flow from the independent to the dependent variable. In the absence of these conditions the method is unreliable.