Probability

• If A and B are mutually exclusive:

  
  

  $P\left(A\cap B\right)$ = 0

  $P\left(A\cup B\right)$ = $P\left(A\right)\ +$$\ P\left(B\right)$
• If A and B are independent:

  
  

  $P\left(A\cap B\right)$ = $P\left(A\right)\ \times P\left(B\right)$

  $P(A|B)$ = $P\left(A\right)$
• What can't you tell from a venn diagram?

  independence
• What's the probability of the labelled area in this venn diagram?

  A) P(B|a)

  
• What's the addition law?

  
  

  $P\left(A\ \cup B\right)$ = $P\left(A\right)\ +$$\ P\left(B\right)\ -\ P\left(A\ \cap B\right)$
• In conditional probability:

  $P(A∣B)=$ $\frac{P\left(A\cap B\right)}{P\left(B\right)}$