CAIE S2 2024 June — Question 3

Exam BoardCAIE
ModuleS2 (Statistics 2)
Year2024
SessionJune
TopicHypothesis test of a normal distribution

3 The time taken in minutes for a certain daily train journey has a normal distribution with standard deviation 5.8. For a random sample of 20 days the journey times were noted and the mean journey time was found to be 81.5 minutes.
  1. Calculate a \(98 \%\) confidence interval for the population mean journey time.
    A student was asked for the meaning of this confidence interval. The student replied as follows.
    'The times for \(98 \%\) of these journeys are likely to be within the confidence interval.'
  2. Explain briefly whether this statement is true or not.
    Two independent 98\% confidence intervals are found.
  3. Given that at least one of these intervals contains the population mean, find the probability that both intervals contain the population mean.