The Venn diagram shows the information from the survey. 13 people have got a dog. The circle for the set of people with a dog has 5 people who just have a dog and 8 people who have both a cat and ...

The man who invented the elegant overlapping circle diagrams would have been 180 today. Infographic: Which Flu Strain Is Most Likely To Bring The Apocalypse? H1N1? Bird flu? Swine flu? Confused?