OCR S4 2008 June — Question 3

Exam BoardOCR
ModuleS4 (Statistics 4)
Year2008
SessionJune
TopicDiscrete Random Variables
TypeJoint distribution with marginal/conditional probabilities

3 From the records of Mulcaster United Football Club the following distribution was suggested as a probability model for future matches. \(X\) and \(Y\) denoted the numbers of goals scored by the home team and the away team respectively.
\(X\)
\cline { 2 - 5 } \multicolumn{1}{c}{}0123
00.110.040.060.08
10.080.050.120.05
20.050.080.070.03
30.030.060.070.02
Use the model to find
  1. \(\mathrm { E } ( X )\),
  2. the probability that the away team wins a randomly chosen match,
  3. the probability that the away team wins a randomly chosen match, given that the home team scores. One of the directors, an amateur statistician, finds that \(\operatorname { Cov } ( X , Y ) = 0.007\). He states that, as this value is very close to zero, \(X\) and \(Y\) may be considered to be independent.
  4. Comment on the director's statement.