When drawing a line of best fit it to a set of data pointsis important to realise that the line should

1. Pass through the centre of the pointswhereis the mean of the x values andis the mean of the y values.

2. Should have as many points – or as close as possible - above the line of best fit as below, with as far as possible no cluster of points above or below.

3. Should not necessarily pass through the origin.

A set of data points and the mean of the data pointsis shown below.

A line of best fit is shown in black below. The lines drawn in red are not lines of best firt.

Line 1 does not pass through the centre of the points and has all but one point lie on or above the line, and line 2 is above most points on the right and below most points on the left in an attempt to make it pass through the origin.