bartlettTests: Bartlett Tests of Homogeneity of Variances

In heplots: Visualizing Hypothesis Tests in Multivariate Linear Models

Bartlett Tests of Homogeneity of Variances

Description

This function extends bartlett.test to a multivariate response setting. It performs the Bartlett test of homogeneity of variances for each of a set of response variables, and prints a compact summary.

Bartlett's test is the univariate version of Box's M test for equality of covariance matrices. This function provides a univariate follow-up test to Box's M test to give one simple assessment of which response variables contribute to significant differences in variances among groups.

Usage

bartlettTests(y, ...)

## Default S3 method:
bartlettTests(y, group, ...)

## S3 method for class 'formula'
bartlettTests(y, data, ...)

## S3 method for class 'lm'
bartlettTests(y, ...)

Arguments

y	A data frame or matrix of numeric response variables for the default method, or a model formula for a multivariate linear model, or the multivariate linear model itself. In the case of a formula or model, the variables on the right-hand-side of the model must all be factors and must be completely crossed.
...	other arguments, passed to bartlett.test
group	a vector or factor object giving the group for the corresponding elements of the rows of y for the default method
data	the data set, for the formula method

Value

An object of classes "anova" and "data.frame", with one observation for each response variable in y.

Author(s)

Michael Friendly

References

Bartlett, M. S. (1937). Properties of sufficiency and statistical tests. Proceedings of the Royal Society of London Series A, 160, 268-282.

See Also

boxM for Box's M test for all responses together.

Examples

bartlettTests(iris[,1:4], iris$Species)

data(Skulls, package="heplots")
bartlettTests(Skulls[,-1], Skulls$epoch)

# formula method
bartlettTests(cbind(mb, bh, bl, nh) ~ epoch, data=Skulls)

heplots documentation built on June 8, 2025, 10:59 a.m.