OCR S4 2011 June — Question 5

Exam BoardOCR
ModuleS4 (Statistics 4)
Year2011
SessionJune
TopicWilcoxon tests

5 A test was carried out to compare the breaking strengths of two brands of elastic band, \(A\) and \(B\), of the same size. Random samples of 6 were selected from each brand and the breaking strengths were measured. The results, in suitable units and arranged in ascending order for each brand, are as follows.
Brand \(A :\)5.68.79.210.711.212.6
Brand \(B :\)10.111.612.012.212.913.5
  1. Give one advantage that a non-parametric test might have over a parametric test in this context.
  2. Carry out a suitable Wilcoxon test at the \(5 \%\) significance level of whether there is a difference between the average breaking strengths of the two brands.
  3. An extra elastic band of brand \(B\) was tested and found to have a breaking strength exceeding all of the other 12 bands. Determine whether this information alters the conclusion of your test.