Edexcel IGCSE Maths 复习笔记 6.5.1 Probability - Venn Diagrams

What is a venn diagram?

• Venn diagrams allow us to show two (or more) characteristics of a situation where there is overlap between the characteristics
• For example, students in a VI Form can study Biology or Chemistry but there may be students who study both

What do I need to know?

• You can be asked to draw a Venn diagram and/or interpret a Venn diagram
• Strictly speaking the rectangle (box) is always essential on a Venn diagram as it represents everything that can happen in the situation
• You may see the letters ε or ζ written inside or just outside the box – this means “the set of all possible outcomes” – basically it just means “everything”!
• The words AND and OR become very important in both drawing and interpreting Venn diagrams
• You will need to be familiar with the symbols ∩ and ∪ – intersection and union, loosely speaking these mean AND and OR (respectively)

1. Drawing a Venn Diagram

• You’ll need a “box” and overlapping “bubbles” depending on how many characteristics you are dealing with
• You will not normally be given all the values for every section in your diagram
• You will be expected to work out missing information in order to complete your Venn diagram
• Remember to consider AND and OR

2. Interpretation

• This is where “not A” (A’) and similar probability that event A does not happen can get confusing
• The symbols ∩ and ∪ are often used here too