There are various clues that can lead to questioning the accuracy of a graphical representation.
The scale on the horizontal axis may have the units unevenly spaced or the vertical axis may not start at 0 when recording frequency.
In some graphs, the area of bars may be meant to represent frequency but may not be proportional to the frequency represented in different bars.
In pie charts, where the circle is meant to represent 100% of the data, the segments of the pie may be incorrectly labelled and not add up to 100%.
One of the most common ways for graphs to be misleading is with the inconsistent use of scale.
Teaching scales in graphs
When presenting graphs from the media it is important to emphasise the context as well as particular misleading features. Often confusion is created from misuse of scale.
Misuse of area
One way for graphs to be misleading is to use an area representation that is not proportional to the value or frequency being represented.
Teaching area for graphs
In presenting graphs from the media to students it is important to emphasise the context as well as particular misleading features. Often area is not used correctly to represent frequency.
Area in graphs
The focus of considering the graph presented here is the importance of the area of each portion of a bar representing the value or frequency of the variable plotted.
The activity for an example of a graph with a misleading scale is based on discussion questions and then a redrawn graph.