OR and AND Problems

• P(A or B) = P(A) + P(B) - P(A and B)
  • This is just a two set Venn diagram problem
  • n(A ∪ B)
  • Problems usually contain the word or
  • Usually a single event
• Two events are mutually exclusive if P(A and B) = 0
• P(A and B) = P(A)*P(B)
  • Normally involves two different experiments or events
  • Problems usually do not involve the word and.
• Experiments are done with replacement and without replacement.
• P(E happening at least once) = 1-P(E does not happen)
• Two events are independent if the occurrence of one does not effect the occurrence of another.
  • Tossing two dice are independent
  • Drawing two cards are dependent
• Do Problems (P 778) 6.11, 16, 18, 19, 21-26, 29, 48, 65, 88,

Conditional Probability

• Given two events E₁ and E₂, if we know E₁ occurred, does this effect the probability that E₂ will occur?
• P(E₂|E₁) = n(E₁ and E₂)/n(E₁)
• P787 do numbers 5, 11, 41-46