OCR MEI D1 2011 June — Question 3

Exam BoardOCR MEI
ModuleD1 (Decision Mathematics 1)
Year2011
SessionJune
TopicPermutations & Arrangements
TypeAssignment/allocation matching problems

3 John has a standard die in his pocket (ie a cube with its six faces labelled from 1 to 6).
  1. Describe how John can use the die to obtain realisations of the random variable \(X\), defined below.
    \(x\)123
    \(\operatorname { Probability } ( X = x )\)\(\frac { 1 } { 2 }\)\(\frac { 1 } { 6 }\)\(\frac { 1 } { 3 }\)
  2. Describe how John can use the die to obtain realisations of the random variable \(Y\), defined below.
    \(y\)123
    \(\operatorname { Probability } ( Y = y )\)\(\frac { 1 } { 2 }\)\(\frac { 1 } { 4 }\)\(\frac { 1 } { 4 }\)
  3. John attempts to use the die to obtain a realisation of a uniformly distributed 2-digit random number. He throws the die 20 times. Each time he records one less than the number showing. He then adds together his 20 recorded numbers. Criticise John's methodology.