In many cases, we encounter data which isn't exactly linear, but which can be approximated or "fit" by a line. This line of best fit is called the least-squares regression line, or sometimes least-squares line.
The regression line is defined as the line where the sum of the squares of the vertical distances of the points to the line are minimized.
Example 6.2.b:
The following graph plots the median weekly earning of full-time
wage and salary workers 25 years of age and older who havehad four years or
more of college, for years between 1980 and 2000.
The plotted data does not represent an exact linear relationship, but it looks
to be suitable for modeling with a regression line.
The regression line for the data is: S = 24.61*t - 48352
Although there are formulas to find lines of best fit, we will not discuss them here. Excel also has several options for creating them.