CAIE S2 2009 November — Question 6

Exam BoardCAIE
ModuleS2 (Statistics 2)
Year2009
SessionNovember
TopicHypothesis test of a normal distribution

6 Photographers often need to take many photographs of families until they find a photograph which everyone in the family likes. The number of photographs taken until obtaining one which everybody likes has mean 15.2. A new photographer claims that she can obtain a photograph which everybody likes with fewer photographs taken. To test at the \(10 \%\) level of significance whether this claim is justified, the numbers of photographs, \(x\), taken by the new photographer with a random sample of 60 families are recorded. The results are summarised by \(\Sigma x = 890\) and \(\Sigma x ^ { 2 } = 13780\).
  1. Calculate unbiased estimates of the population mean and variance of the number of photographs taken by the new photographer.
  2. State null and alternative hypotheses for the test, and state also the probability that the test results in a Type I error. Say what a Type I error means in the context of the question.
  3. Carry out the test.