hov: Homogeneity of Variance

Description Usage Arguments Value Author(s) References See Also Examples

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

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hov(x, data=NULL, 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 (2015). Statistical Analysis and Data Display: An Intermediate Course with Examples in R. Second Edition. Springer-Verlag, New York. https://www.springer.com/us/book/9781493921218

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

See Also

aov, hovPlot

Examples

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data(turkey)

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

Example output

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

	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

HH documentation built on Nov. 28, 2020, 9:06 a.m.

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