Package org.apache.commons.statistics.inference

Class OneWayAnova

java.lang.Object

org.apache.commons.statistics.inference.OneWayAnova

public final class OneWayAnova
extends Object

Implements one-way ANOVA (analysis of variance) statistics.

Tests for differences between two or more categories of univariate data (for example, the body mass index of accountants, lawyers, doctors and computer programmers). When two categories are given, this is equivalent to the TTest.

This implementation computes the F statistic using the definitional formula:

\[ F = \frac{\text{between-group variability}}{\text{within-group variability}} \]

Since:

1.1

See Also:

Analysis of variance (Wikipedia), Multiple-comparison ANOVA problems (Wikipedia), McDonald, J.H. 2014. Handbook of Biological Statistics (3rd ed.). Sparky House Publishing, Baltimore, Maryland. One-way anova. pp 145-156.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	OneWayAnova.Result	Result for the one-way ANOVA.

Method Summary

Modifier and Type	Method	Description
double	statistic(Collection<double[]> data)	Computes the F statistic for an ANOVA test for a collection of category data, evaluating the null hypothesis that there is no difference among the means of the data categories.
OneWayAnova.Result	test(Collection<double[]> data)	Performs an ANOVA test for a collection of category data, evaluating the null hypothesis that there is no difference among the means of the data categories.
static OneWayAnova	withDefaults()	Return an instance using the default options.

Methods inherited from class java.lang.Object

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

Method Detail

withDefaults

public static OneWayAnova withDefaults()

Return an instance using the default options.

Returns:

default instance

statistic

public double statistic(Collection<double[]> data)

Computes the F statistic for an ANOVA test for a collection of category data, evaluating the null hypothesis that there is no difference among the means of the data categories.

Special cases:

• If the value in each category is the same (no variance within groups) but different between groups, the f-value is infinity.
• If the value in every group is the same (no variance within or between groups), the f-value is NaN.

Parameters:

data - Category summary data.

Returns:

F statistic

Throws:

IllegalArgumentException - if the number of categories is less than two; a contained category does not have at least one value; or all categories have only one value (zero degrees of freedom within groups)

test

public OneWayAnova.Result test(Collection<double[]> data)

Performs an ANOVA test for a collection of category data, evaluating the null hypothesis that there is no difference among the means of the data categories.

Special cases:

• If the value in each category is the same (no variance within groups) but different between groups, the f-value is infinity and the p-value is zero.
• If the value in every group is the same (no variance within or between groups), the f-value and p-value are NaN.

Parameters:

data - Category summary data.

Returns:

test result

Throws:

IllegalArgumentException - if the number of categories is less than two; a contained category does not have at least one value; or all categories have only one value (zero degrees of freedom within groups)