What makes a clear graph?

As we saw in the example, it is important to be able to look at a graph and figure out if its data is presented in a clear way.

Let us look at two graphs that present the same information on house prices rising:

Graph 1

A graph showing how the average house price has increased from £80,000 in 1998 to £82,000 in 1999

Graph 1 presents data in a way that makes it look like there was an increase of 200% between 1998 and 1999 because the second bar is three times the size of the first bar.

The scale on the left is not the first thing we are drawn to. However, if you look closely the increase is from £80, 000 - £82, 000. This is actually only an increase of 2.5%.

The way this graph presents data is misleading. It is also inaccurate as the box from zero to £80, 000 is the same height as £80, 000 - £81, 000.

Graph 2

The same graph showing how the average house price has increased from £80,000 in 1998 to £82,000 in 1999, however, the y-axis begins at zero

Graph 2 presents the data in a way that indicates a small increase between 1998 and 1999. As we have seen, the increase is only 2.5%. As this graph represents a small percentage increase with a small increase on the graph, this graph would be a more acurate, less misleading way to present this data.

Data handlingWhat makes a clear graph?