| Exam Board | OCR |
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| Module | S4 (Statistics 4) |
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| Year | 2015 |
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| Session | June |
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| Topic | Wilcoxon tests |
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6 In a two-tail Wilcoxon rank-sum test, the sample sizes are 13 and 15. The sum of the ranks for the sample of size 13 is 135 . Carry out the test at the \(5 \%\) level of significance.