CAIE S2 2017 November — Question 2

Exam BoardCAIE
ModuleS2 (Statistics 2)
Year2017
SessionNovember
TopicLinear combinations of normal random variables
TypeSample size determination

2 The number of words in History essays by students at a certain college has mean \(\mu\) and standard deviation 1420.
  1. The mean number of words in a random sample of 125 History essays was found to be 4820 . Calculate a \(98 \%\) confidence interval for \(\mu\).
  2. Another random sample of \(n\) History essays was taken. Using this sample, a \(95 \%\) confidence interval for \(\mu\) was found to be 4700 to 4980 , both correct to the nearest integer. Find the value of \(n\).