org.statcato.statistics.inferential.nonparametrics

Class WilcoxonRankSumTest

java.lang.Object

org.statcato.statistics.inferential.nonparametrics.WilcoxonRankSumTest

public class WilcoxonRankSumTest
extends java.lang.Object

Wilcoxon Rank Sum test. A nonparametic test that uses ranks of samples from two independent populations to test a claim about the medians of two populations. The two independent samples are combined into one sample, are sorted in ascending order and are ranked based on its place in the one sample. The sum of the ranks corresponding to one of the two samples are computed and is used as test statistics.

Since:

1.0

Field Summary

Fields

Modifier and Type	Field and Description
double	significance Significance of the test.

Constructor Summary

Constructors

Constructor and Description
WilcoxonRankSumTest(java.util.Vector<java.lang.Double> data1, java.util.Vector<java.lang.Double> data2, int testType, double significance) Constructor, given two samples of data values.

Method Summary

Modifier and Type	Method and Description
double	criticalValue_R()
double	getRankSum(java.util.Vector<java.lang.Double> data1, java.util.Vector<java.lang.Double> data2) Returns the rank sum, which is the sum of ranks for the first sample.
double	mu_R() Returns the mean of the distribution of rank sum, mu = n1 * (n1 + n2 + 1) / 2.
double	pValue_R() Returns the p-value.
double	sigma_R() Returns the standard deviation of the distribution of rank sum, sigma = (n1 * n2 * (n1 + n2 + 1) / 12)^0.5
double	testStatistic_R() Returns the test statistic z = (R - mu) / sigma, where R is the rank sum of the first same, mu the mean of the distribution of rank sum, and sigma the standard deviatioin of the distribution of rank sum.
java.lang.String	toString()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

significance

public double significance

Significance of the test.

Constructor Detail

WilcoxonRankSumTest

public WilcoxonRankSumTest(java.util.Vector<java.lang.Double> data1,
                           java.util.Vector<java.lang.Double> data2,
                           int testType,
                           double significance)

Constructor, given two samples of data values.

Parameters:

data1 - vector of double values (sample 1)

data2 - vector of double values (sample 2)

testMedian - hypothesized median

testType - type of alternative hypothesis

Method Detail

testStatistic_R

public double testStatistic_R()

Returns the test statistic z = (R - mu) / sigma, where R is the rank sum of the first same, mu the mean of the distribution of rank sum, and sigma the standard deviatioin of the distribution of rank sum.

Returns:

test statistic z

mu_R

public double mu_R()

Returns the mean of the distribution of rank sum, mu = n1 * (n1 + n2 + 1) / 2.

Returns:

mean

sigma_R

public double sigma_R()

Returns the standard deviation of the distribution of rank sum, sigma = (n1 * n2 * (n1 + n2 + 1) / 12)^0.5

Returns:

standard deviation

pValue_R

public double pValue_R()

Returns the p-value.

Returns:

p-value

criticalValue_R

public double criticalValue_R()

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

getRankSum

public double getRankSum(java.util.Vector<java.lang.Double> data1,
                         java.util.Vector<java.lang.Double> data2)

Returns the rank sum, which is the sum of ranks for the first sample. Ranks are computed after the two samples are combined and sorted in ascending order.

Parameters:

data - vector of Double values

Returns:

rank sum