Line of best fit
A line of best fit is usually drawn on a scatter diagram. It is drawn so that the points are evenly distributed on either side of the line.
There are various methods for drawing this 'precisely' but you'll only be expected to draw the line 'by eye'.
When drawing the line of best fit, use a transparent ruler so that you can see how the line fits between all the points before you draw it.
Example
The heights and weights of twenty children in a class are recorded. The results are shown on the scatter diagram below.
Katie is 148 cm tall. Draw a line of best fit and use it to estimate her weight.
Answer
We start by drawing a line of best fit.
Katie is 148 cm tall, so we draw a straight line up from 148cm on the A line with zero slope. An axis is one of the lines used to locate a point in a coordinate system. until it meets the line of best fit and then along until it meets the At right angles to the ground or horizontal. axis.
Katie weighs approximately 52 kg.
As you're only drawing the line of best fit 'by eye', it's unlikely your answer will be the same as that of your friend.
Another way of getting an estimate is to use the equation of the line of best fit.