com.numericalmethod.suanshu.stats.test.variance

Class Bartlett

java.lang.Object

com.numericalmethod.suanshu.stats.test.HypothesisTest

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

All Implemented Interfaces:

java.io.Serializable

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

, Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
double	df the degree of freedom

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

k, N, pValue, testStatistics

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
java.lang.String	getAlternativeHypothesis() Get a description of the alternative hypothesis.
java.lang.String	getNullHypothesis() Get a description of the null hypothesis.

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

isNullRejected, oneSidedPvalue, pValue, statistics

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

getNullHypothesis

public java.lang.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

See Also:

Wikipedia: Null hypothesis

getAlternativeHypothesis

public java.lang.String getAlternativeHypothesis()

Description copied from class: HypothesisTest

Get a description of the alternative hypothesis.

Specified by:

getAlternativeHypothesis in class HypothesisTest

Returns:

the alternative hypothesis description

See Also:

Wikipedia: Alternative hypothesis