Lines of best fit

When all the points line up perfectly in a graph, it’s easy just to draw a straight line through them, like this:

However, surprise surprise, points don’t always line up this nicely.  When they don’t, you need a way of drawing a line through the data to represent what you think the trend in the data is.  There are lots of different ways of doing this.  One of the simplest is a line of best fit.  We’ll use this graph to show how to do it: