org.moeaframework.util.statistics
Class TwoSampleTTest

java.lang.Object
  org.moeaframework.util.statistics.IntervalRatioStatisticalTest
      org.moeaframework.util.statistics.TwoSampleTTest

All Implemented Interfaces:

StatisticalTest

public class TwoSampleTTest
extends IntervalRatioStatisticalTest

The Two-Sample t test determines if the mean of two populations are different. The independent flag in the constructor is used to choose between the unpaired (independent) and paired (dependent) test.

• Null Hypothesis: The two population means are equal.
• Alternative Hypothesis: The two population means are not equal.

Assumptions:

1. Samples are randomly selected from the corresponding population
2. The distribution of the underlying populations is normal

References:

1. 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.IntervalRatioStatisticalTest

data, numberOfGroups

Constructor Summary

TwoSampleTTest(boolean independent)
Constructs a two sample T test.

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.IntervalRatioStatisticalTest

categorize, getNumberOfGroups

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TwoSampleTTest

public TwoSampleTTest(boolean independent)

Constructs a two sample T test.

Parameters:

independent - uses the unpaired T test if true; the paired T test if false

Method Detail

add

public void add(double value,
                int group)

Description copied from class: IntervalRatioStatisticalTest

Adds a new observation with the specified value and group.

Overrides:

add in class IntervalRatioStatisticalTest

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: IntervalRatioStatisticalTest

Adds several new observations to the specified group.

Overrides:

addAll in class IntervalRatioStatisticalTest

Parameters:

values - the values of the new observations

group - the group to which the new observations belong

test

public boolean test(double alpha)

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

See Also:

TestUtils.tTest(double[], double[], double), TestUtils.pairedTTest(double[], double[], double)