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 ANOVA, assume that variances are equal across groups or samples. A homoscedasticity test, such as 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

Constructor Summary

Bartlett(double[]... samples)
Perform the Bartlett test to test for equal variances across the groups.

Method Summary

java.lang.String	getAlternativeHypothesis() Get the description of the alternative hypothesis.
java.lang.String	getNullHypothesis() Get a description of the null hypothesis.
double	pValue() Get the p-value for the test statistics.
double	statistics() Get the test statistics.

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

isNullRejected, nGroups, nObs, oneSidedPvalue

Methods inherited from class java.lang.Object

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

Constructor Detail

Bartlett

public Bartlett(double[]... samples)

Perform the Bartlett test to test for equal variances across the groups.

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 the description of the alternative hypothesis.

Specified by:

getAlternativeHypothesis in class HypothesisTest

Returns:

the alternative hypothesis description

See Also:

Wikipedia: Alternative hypothesis

statistics

public double statistics()

Description copied from class: HypothesisTest

Get the test statistics.

Specified by:

statistics in class HypothesisTest

Returns:

the test statistics

See Also:

Wikipedia: Test statistic

pValue

public double pValue()

Description copied from class: HypothesisTest

Get the p-value for the test statistics.

Specified by:

pValue in class HypothesisTest

Returns:

the p-value

See Also:

Wikipedia: P-value