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Last data update: 2014.03.03

R: Homogeneity of Variance

hov	R Documentation

Homogeneity of Variance

Description

Oneway analysis of variance makes the assumption that the variances of the groups are equal. Brown and Forsyth, 1974 present the recommended test of this assumption. The Brown and Forsyth test statistic is the F statistic resulting from an ordinary one-way analysis of variance on the absolute deviations from the median.

Usage

hov(x, data = sys.parent(), method = "bf") ## x is a formula

## users will normally use the formula above and will not call the
## method directly.
hov.bf(x, group,  ## x is the response variable
       y.name = deparse(substitute(x)),
       group.name = deparse(substitute(group)))

Arguments

`x`	Formula appropriate for oneway anova in `hov`. Response variable in `hov.bf`.
`data`	data.frame
`method`	Character string defining method. At this time the only recognized method is `"bf"` for the Brown–Forsyth method.
`group`	factor.
`y.name`	name of response variable, defaults to variable name in formula.
`group.name`	name of factor, defaults to variable name in formula.

Value

"htest" object for the hov test.

Author(s)

Richard M. Heiberger <rmh@temple.edu>

References

Heiberger, Richard M. and Holland, Burt (2004b). Statistical Analysis and Data Display: An Intermediate Course with Examples in S-Plus, R, and SAS. Springer Texts in Statistics. Springer. ISBN 0-387-40270-5.

Brown, M.~B. and Forsyth, A.~B. (1974). Robust tests for equality of variances. Journal of the American Statistical Association, 69:364–367.

Examples

data(turkey)

hov(wt.gain ~ diet, data=turkey)
hovPlot(wt.gain ~ diet, data=turkey)

Results


R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

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Type 'license()' or 'licence()' for distribution details.

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Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
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Type 'q()' to quit R.

> library(HH)
Loading required package: lattice
Loading required package: grid
Loading required package: latticeExtra
Loading required package: RColorBrewer
Loading required package: multcomp
Loading required package: mvtnorm
Loading required package: survival
Loading required package: TH.data
Loading required package: MASS

Attaching package: 'TH.data'

The following object is masked from 'package:MASS':

    geyser

Loading required package: gridExtra
> png(filename="/home/ddbj/snapshot/RGM3/R_CC/result/HH/hov.Rd_%03d_medium.png", width=480, height=480)
> ### Name: hov
> ### Title: Homogeneity of Variance
> ### Aliases: hov hov.bf
> ### Keywords: models
> 
> ### ** Examples
> 
> data(turkey)
> 
> hov(wt.gain ~ diet, data=turkey)

	hov: Brown-Forsyth

data:  wt.gain
F = 2.2257, df:diet = 4, df:Residuals = 25, p-value = 0.09506
alternative hypothesis: variances are not identical

> hovPlot(wt.gain ~ diet, data=turkey)
> 
> 
> 
> 
> 
> dev.off()
null device 
          1 
>