OCR S4 2016 June — Question 5

Exam BoardOCR
ModuleS4 (Statistics 4)
Year2016
SessionJune
TopicConditional Probability
TypeComplement and union/intersection laws

5 Events \(A\) and \(B\) are such that \(\mathrm { P } ( A ) = 0.5 , \mathrm { P } ( B ) = 0.6\) and \(\mathrm { P } \left( A \mid B ^ { \prime } \right) = 0.75\).
  1. Find \(\mathrm { P } ( A \cap B )\) and \(\mathrm { P } ( A \cup B )\).
  2. Determine, giving a reason in each case,
    (a) whether \(A\) and \(B\) are mutually exclusive,
    (b) whether \(A\) and \(B\) are independent.
  3. A further event \(C\) is such that \(\mathrm { P } ( A \cup B \cup C ) = 1\) and \(\mathrm { P } ( A \cap B \cap C ) = 0.05\). It is also given that \(\mathrm { P } \left( A \cap B ^ { \prime } \cap C \right) = \mathrm { P } \left( A ^ { \prime } \cap B \cap C \right) = x\) and \(\mathrm { P } \left( A \cap B ^ { \prime } \cap C ^ { \prime } \right) = 2 x\).
    Find \(\mathrm { P } ( C )\).