A line of best fit, also known as a regression line, is a line of fit that estimates the relationship between the values of a data set. The equation of the line of best fit has been determined using a strict mathematical method.

One commonly used method to determine a line of best fit is the method of least squares. The methods used to find the line of best fit are usually hard to do by hand. Therefore, a line of best fit can be found by performing a linear regression on a graphing calculator. As an example, consider the data set graphed above.

$x$	$y$
$0.6$	$1.5$
$1.2$	$3.6$
$2.6$	$5.2$
$3.6$	$6.3$
$4.5$	$8.7$
$6$	$10.3$
$6.6$	$11.8$
$7.1$	$11.7$

In reference to the graph, the data points appear to closely follow the line $y=1.55x+1.14.$ Consequently, even if the data points may not precisely align with any specific line, a linear model can be considered to adequately describe the data.