# SuanShu, a Java numerical and statistical library

com.numericalmethod.suanshu.stats.test.rank

## Class KruskalWallis

• public class KruskalWallis
extends HypothesisTest
The Kruskal-Wallis test is a non-parametric method for testing the equality of population medians among groups. It is identical to a one-way analysis of variance with the data replaced by their ranks. Since it is a non-parametric method, the Kruskal-Wallis test does not assume a normal population, unlike the analogous one-way analysis of variance. However, the test does assume an identically-shaped and scaled distribution for each group, except for any difference in medians.

TODO: correction for ties

The R equivalent function is kruskal.test.

Wikipedia: Kruskal-Wallis one-way analysis of variance
• ### Constructor Summary

Constructors
Constructor and Description
KruskalWallis(double[]... samples)
Construct a Kruskal-Wallis test for the equality of medians of groups.
• ### Method Summary

All Methods
Modifier and Type Method and Description
String getAlternativeHypothesis()
Get the description of the alternative hypothesis.
String getNullHypothesis()
Get a description of the null hypothesis.
double pValue()
Get the p-value for the test statistics.
double statistics()
Get the test statistics.
• ### Methods inherited from class com.numericalmethod.suanshu.stats.test.HypothesisTest

isNullRejected, nGroups, nObs, oneSidedPvalue
• ### Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
• ### Constructor Detail

• #### KruskalWallis

public KruskalWallis(double[]... samples)
Construct a Kruskal-Wallis test for the equality of medians of groups.
Parameters:
samples - samples
• ### Method Detail

• #### getNullHypothesis

public String getNullHypothesis()
Description copied from class: HypothesisTest
Get a description of the null hypothesis.
Specified by:
getNullHypothesis in class HypothesisTest
Returns:
the null hypothesis description
Wikipedia: Null hypothesis
• #### getAlternativeHypothesis

public String getAlternativeHypothesis()
Description copied from class: HypothesisTest
Get the description of the alternative hypothesis.
Specified by:
getAlternativeHypothesis in class HypothesisTest
Returns:
the alternative hypothesis description
Wikipedia: Alternative hypothesis
• #### statistics

public double statistics()
Description copied from class: HypothesisTest
Get the test statistics.
Specified by:
statistics in class HypothesisTest
Returns:
the test statistics
Wikipedia: Test statistic
• #### pValue

public double pValue()
Description copied from class: HypothesisTest
Get the p-value for the test statistics.
Specified by:
pValue in class HypothesisTest
Returns:
the p-value