Practice with inclusion, exclusion.

Events \(A\), \(B\), and \(C\) are defined on a probability space. Find expressions for the
following probabilities in terms of \(\mathbf{P}(A)\), \(\mathbf{P}(B)\), \(\mathbf{P}(C)\), \(\mathbf{P}(AB)\), \(\mathbf{P}(AC)\), \(\mathbf{P}(BC)\), and \(\mathbf{P}(ABC)\).

  1. The probability that exactly two of the \(A\), \(B\), \(C\) occur.
  2. The probability that exactly one of these events occurs.
  3. The probability that none of these events occur.

Here the notation \(AB\) is short for \(A \cap B\) which is the event “both \(A\) and \(B\)”

( [Pitman, p. 31, # 10])

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