A pie chart compares parts to a whole. As such it shows a percentage distribution. The entire pie represents the total data set and each segment of the pie is a particular category within the whole.
So, to use a pie chart, the data you are measuring must depict a ratio or percentage relationship. You must always use the same unit of measure within a pie chart. Otherwise your numbers will mean nothing.
The pie chart in Figure 8 shows where ABC Enterprise’s sales come from
Tip 1:
Be careful not to use too many segments in your pie chart. More than about six and it gets far too crowded. Here it is better to use a bar chart instead.
Tip 2:
If you want to emphasize one of the segments, you can detach it a bit from the main pie. This visual separation makes it stand out.
Tip 3:
For all their obvious usefulness, pie charts do have limitations, and can be misleading.
2.3.5. Venn Diagram
The last graph we will cover here is the Venn diagram. Devised by the mathematician John Venn in 1881, this is a diagram used to show overlaps between sets of data.
Each set is represented by a circle. The degree of overlap between the sets is depicted by the overlap between circles.
Figure 9 shows sales at Perfect Printing. There are three product lines: stationery printing, newsletter printing, and customised promotional items such as mugs.
By separating out the proportions of the business’ customers that buy each type of product, it becomes clear that the majority of the biggest group of customers (55% of the total) – those who have their company stationery printed – are only using Perfect Printing for stationery. It’s possible that they don’t realise that Perfect Printing could also print their company newsletters and promotional items. As a result, Perfect Printing should consider designing some marketing activity to promote these product lines to its stationery customers.
Customers who get their newsletters printed by Perfect Printing, on the other hand, seem to be well aware that the company also offers stationery printing and promotional items.
A Venn diagram is a great choice to use when you are trying to convey the amount of commonality or difference between distinct groups.
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