Edexcel S1 2024 June — Question 2

Exam BoardEdexcel
ModuleS1 (Statistics 1)
Year2024
SessionJune
TopicDiscrete Probability Distributions
TypeDirect probability from given distribution

2. A spinner can land on the numbers \(2,4,5,7\) or 8 only. The random variable \(X\) represents the number that this spinner lands on when it is spun once. The probability distribution of \(X\) is given in the table below.
\(\boldsymbol { x }\)24578
\(\mathbf { P } ( \boldsymbol { X } = \boldsymbol { x } )\)0.250.30.20.10.15
  1. Find \(\mathrm { P } ( 2 X - 3 > 5 )\) Given that \(\mathrm { E } ( X ) = 4.6\)
  2. show that \(\operatorname { Var } ( X ) = 4.14\) The random variable \(Y = a X - b\) where \(a\) and \(b\) are positive constants.
    Given that $$\mathrm { E } ( Y ) = 13.4 \quad \text { and } \quad \operatorname { Var } ( Y ) = 66.24$$
  3. find the value of \(a\) and the value of \(b\) In a game Sam and Alex each spin the spinner once, landing on \(X _ { 1 }\) and \(X _ { 2 }\) respectively.
    Sam's score is given by the random variable \(S = X _ { 1 }\)
    Alex's score is given by the random variable \(R = 2 X _ { 2 } - 3\)
    The person with the higher score wins the game. If the scores are the same it is a draw.
  4. Find the probability that Sam wins the game.