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IB Maths AA SL 4.11 Formal Conditional Probability

IB Maths AA SL 4.11 Formal Conditional Probability
IB Mathematics: analysis and approaches guide, first assessment 2021

Practise formal conditional probability by defining the restricted sample space, finding the matching intersection and using the result to test independence or compare sources.

How this is tested

  • calculate P(A|B) as P(A ∩ B)/P(B) with the conditioning event as denominator
  • translate given that wording into a conditional event before using a tree, Venn diagram or model
  • test independence by comparing P(A|B) with P(A) or an intersection with the product

Question 3(c)

[Maximum number: 3]

Two events A and B are such that P(A)=0.5, P(B)=0.6 and P(A∩B)=0.4\mathrm{P}(A \cap B)=0.4.

Find P(A∣B′)\mathrm{P}\left(A \mid B^{\prime}\right).