CAIE S2 2012 June — Question 7

Exam BoardCAIE
ModuleS2 (Statistics 2)
Year2012
SessionJune
TopicHypothesis test of a normal distribution

7 The weights, \(X\) kilograms, of bags of carrots are normally distributed. The mean of \(X\) is \(\mu\). An inspector wishes to test whether \(\mu = 2.0\). He weighs a random sample of 200 bags and his results are summarised as follows. $$\Sigma x = 430 \quad \Sigma x ^ { 2 } = 1290$$
  1. Carry out the test, at the \(10 \%\) significance level.
  2. You may now assume that the population variance of \(X\) is 1.85 . The inspector weighs another random sample of 200 bags and carries out the same test at the \(10 \%\) significance level.
    (a) State the meaning of a Type II error in this context.
    (b) Given that \(\mu = 2.12\), show that the probability of a Type II error is 0.652 , correct to 3 significant figures.