The Fit Linear dialog box is used to perform linear regression and fits a straight line to a given data set. The fitting model is written as
where 
is the y intercept, 
is the slope and 
is the error term. The error term represents the unexplained variation in the dependent variable and is usually assumed to have a mean of zero.
To estimate the parameters, the chi-square minimization or "weighted least-square" method is used. The goal is to minimize the sum of the squares of the deviations between the theoretical curve and the experimental points for a range of independent variables. After fitting, the model is evaluated using hypothesis tests and plotting of residuals.