com.numericalmethod.suanshu.stats.test.variance
Class Bartlett

java.lang.Object
  com.numericalmethod.suanshu.stats.test.HypothesisTest
      com.numericalmethod.suanshu.stats.test.variance.Bartlett

public class Bartlett
extends HypothesisTest

Bartlett's test is used to test if k samples are from populations with equal variances, hence homoscedasticity. Some statistical tests, for example the analysis of variance, assume that variances are equal across groups or samples. The Bartlett test can be used to verify that assumption.

Bartlett's test is sensitive to departures from normality. That is, if the samples come from non-normal distributions, then Bartlett's test may simply be testing for non-normality. The Levene and BrownForsythe tests are alternatives to the Bartlett test that are less sensitive to departures from normality.

The R equivalent function is bartlett.test.

See Also:

• Wikipedia: Bartlett's test
• Engineer Statistics handbook

Field Summary

double

df the degree of freedom

Fields inherited from class com.numericalmethod.suanshu.stats.test.HypothesisTest

k, N, pValue, testStatistics

Constructor Summary

Bartlett(double[]... samples)
Perform the Bartlett test to test if the samples are from populations with equal variances.

Method Summary

java.lang.String	alternativeHypothesis() Get a description of the alternative hypothesis.
java.lang.String	nullHypothesis() Get a description of the null hypothesis.

Methods inherited from class com.numericalmethod.suanshu.stats.test.HypothesisTest

oneSidedPvalue, pValue, rejectNull, testStatistics

Methods inherited from class java.lang.Object

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

Field Detail

df

public final double df

the degree of freedom

Constructor Detail

Bartlett

public Bartlett(double[]... samples)

Perform the Bartlett test to test if the samples are from populations with equal variances.

Parameters:

samples - samples

Method Detail

nullHypothesis

public java.lang.String nullHypothesis()

Description copied from class: HypothesisTest

Get a description of the null hypothesis.

Specified by:

nullHypothesis in class HypothesisTest

Returns:

the null hypothesis description

See Also:

Wikipedia: Null hypothesis

alternativeHypothesis

public java.lang.String alternativeHypothesis()

Description copied from class: HypothesisTest

Get a description of the alternative hypothesis.

Specified by:

alternativeHypothesis in class HypothesisTest

Returns:

the alternative hypothesis description

See Also:

Wikipedia: Alternative hypothesis