Multiple linear regression studies the relationship between several predictor variables and a response variable. The model is of the form
where 
, are the coefficients and ? is the error term. The error term represents the unexplained variation in the dependent variable. We assume that the mean of the random variable ? is zero.
Parameters are estimated using a weighted least-square method. After fitting, the model can be evaluated using hypothesis tests and by plotting residuals. In addition, we can employ partial regression plots to study the relationship between the response variable and a given predictor variable.