Edexcel S1 2016 June — Question 5

Exam BoardEdexcel
ModuleS1 (Statistics 1)
Year2016
SessionJune
TopicDiscrete Probability Distributions
TypeSequential trials until success

5. A biased tetrahedral die has faces numbered \(0,1,2\) and 3 . The die is rolled and the number face down on the die, \(X\), is recorded. The probability distribution of \(X\) is
\(x\)0123
\(\mathrm { P } ( X = x )\)\(\frac { 1 } { 6 }\)\(\frac { 1 } { 6 }\)\(\frac { 1 } { 6 }\)\(\frac { 1 } { 2 }\)
If \(X = 3\) then the final score is 3
If \(X \neq 3\) then the die is rolled again and the final score is the sum of the two numbers. The random variable \(T\) is the final score.
  1. Find \(\mathrm { P } ( T = 2 )\)
  2. Find \(\mathrm { P } ( T = 3 )\)
  3. Given that the die is rolled twice, find the probability that the final score is 3