CAIE S2 2018 November — Question 2

Exam BoardCAIE
ModuleS2 (Statistics 2)
Year2018
SessionNovember
TopicHypothesis test of binomial distributions
TypeState hypotheses with additional parts

2 A headteacher models the number of children who bring a 'healthy' packed lunch to school on any day by the distribution \(\mathrm { B } ( 150 , p )\). In the past, she has found that \(p = \frac { 1 } { 3 }\). Following the opening of a fast food outlet near the school, she wishes to test, at the \(1 \%\) significance level, whether the value of \(p\) has decreased.
  1. State the null and alternative hypotheses for this test.
    On a randomly chosen day she notes the number, \(N\), of children who bring a 'healthy' packed lunch to school. She finds that \(N = 36\) and then, assuming that the null hypothesis is true, she calculates that \(\mathrm { P } ( N \leqslant 36 ) = 0.0084\).
  2. State, with a reason, the conclusion that the headteacher should draw from the test.
  3. According to the model, what is the largest number of children who might bring a packed lunch to school?