OCR S3 2010 January — Question 2

Exam BoardOCR
ModuleS3 (Statistics 3)
Year2010
SessionJanuary
TopicLinear combinations of normal random variables
TypeSum or total of normal variables

2 The amount of tomato juice, \(X \mathrm { ml }\), dispensed into cartons of a particular brand has a normal distribution with mean 504 and standard deviation 3 . The juice is sold in packs of 4 cartons, filled independently. The total amount of juice in one pack is \(Y \mathrm { ml }\).
  1. Find \(\mathrm { P } ( Y < 2000 )\). The random variable \(V\) is defined as \(Y - 4 X\).
  2. Find \(\mathrm { E } ( V )\) and \(\operatorname { Var } ( V )\).
  3. What is the probability that the amount of juice in a randomly chosen pack is more than 4 times the amount of juice in a randomly chosen carton?