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Chapter 10: Sorting Out the Means with Multiple Comparisons 189

The Kruskal-Wallis test doesn’t use the actual values of the data; it’s based on
ranks (orderings of the data from smallest to largest). The test ranks all the
data together, and then looks at how those ranks are distributed out amongst
the samples that represent separate populations. If one sample gets all the
small ranks, that population is concluded to have a smaller mean than the
others, and so on. (Turn to Chapter 16 for the full story on nonparametric
statistics and Chapter 19 for all the details of the Kruskal-Wallis test.)

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