MOEA Framework 2.12
API Specification

org.moeaframework.util.statistics
Class KruskalWallisTest

java.lang.Object
  extended by org.moeaframework.util.statistics.OrdinalStatisticalTest
      extended by org.moeaframework.util.statistics.KruskalWallisTest
All Implemented Interfaces:
StatisticalTest

public class KruskalWallisTest
extends OrdinalStatisticalTest

The Kruskal-Wallis One-Way Analysis of Variance by Ranks is a non-parametric statistical test determining if (at least) two out of K >= 2 populations have differing medians.

Assumptions:

  1. Samples are randomly selected from their corresponding populations
  2. Samples are independent
  3. The dependent variable (value being sampled) is continuous
  4. The underlying distributions of the populations are identical in shape

References:

  1. Kruskal, W.H. and Wallis W.A. "Use of Ranks in One-Criterion Variance Analysis." Journal of the American Statistical Association, 47(260):583-621, 1952.
  2. Sheskin, D.J. "Handbook of Parametric and Nonparametric Statistical Procedures, Third Edition." Chapman & Hall/CRC. 2004.


Field Summary
 
Fields inherited from class org.moeaframework.util.statistics.OrdinalStatisticalTest
comparator, data, numberOfGroups
 
Constructor Summary
KruskalWallisTest(int numberOfGroups)
          Constructs a Kruskal-Wallis test with the specified number of groups.
 
Method Summary
 void add(double value, int group)
          Adds a new observation with the specified value and group.
 void addAll(double[] values, int group)
          Adds several new observations to the specified group.
 boolean test(double alpha)
          Returns true if the null hypothesis is rejected; false otherwise.
 
Methods inherited from class org.moeaframework.util.statistics.OrdinalStatisticalTest
getComparator, getNumberOfGroups, size, update
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

KruskalWallisTest

public KruskalWallisTest(int numberOfGroups)
Constructs a Kruskal-Wallis test with the specified number of groups.

Parameters:
numberOfGroups - the number of groups being tested
Method Detail

add

public void add(double value,
                int group)
Description copied from class: OrdinalStatisticalTest
Adds a new observation with the specified value and group.

Overrides:
add in class OrdinalStatisticalTest
Parameters:
value - the value of the new observation
group - the group to which the new observation belongs

addAll

public void addAll(double[] values,
                   int group)
Description copied from class: OrdinalStatisticalTest
Adds several new observations to the specified group.

Overrides:
addAll in class OrdinalStatisticalTest
Parameters:
values - the values of the new observations
group - the group to which the new observations belong

test

public boolean test(double alpha)
Description copied from interface: StatisticalTest
Returns true if the null hypothesis is rejected; false otherwise. The meaning of the null hypothesis and alternative hypothesis depends on the specific test.

The prespecified level of confidence, alpha, can be used for either one-tailed or two-tailed (directional or nondirectional) distributions, depending on the specific test. Some tests may only support specific values for alpha.

Parameters:
alpha - the prespecified level of confidence
Returns:
true if the null hypothesis is rejected; false otherwise

MOEA Framework 2.12
API Specification

Copyright 2009-2016 MOEA Framework. All rights reserved.
Licensed under the GNU Lesser General Public License.
Return to the MOEA Framework homepage. Visit us on Github!