hartleyTest function

Hartley's Maximum F-Ratio Test of Homogeneity of Variances

Performs Hartley's maximum F-ratio test of the null that variances in each of the groups (samples) are the same.

hartleyTest(x, ...)

## Default S3 method:
hartleyTest(x, g, ...)

## S3 method for class 'formula'
hartleyTest(formula, data, subset, na.action, ...)

Arguments

• x: a numeric vector of data values, or a list of numeric data vectors.
• ...: further arguments to be passed to or from methods.
• g: a vector or factor object giving the group for the corresponding elements of "x". Ignored with a warning if "x" is a list.
• formula: a formula of the form response ~ group where response gives the data values and group a vector or factor of the corresponding groups.
• data: an optional matrix or data frame (or similar: see model.frame) containing the variables in the formula formula. By default the variables are taken from environment(formula).
• subset: an optional vector specifying a subset of observations to be used.
• na.action: a function which indicates what should happen when the data contain NAs. Defaults to getOption("na.action").

Returns

A list with class "htest" containing the following components:

• method: a character string indicating what type of test was performed.
• data.name: a character string giving the name(s) of the data.
• statistic: the estimated quantile of the test statistic.
• p.value: the p-value for the test.
• parameter: the parameters of the test statistic, if any.
• alternative: a character string describing the alternative hypothesis.
• estimates: the estimates, if any.
• null.value: the estimate under the null hypothesis, if any.

Details

If x is a list, its elements are taken as the samples to be compared for homogeneity of variances. In this case, the elements must all be numeric data vectors, g is ignored, and one can simply use hartleyTest(x) to perform the test. If the samples are not yet contained in a list, use hartleyTest(list(x, ...)).

Otherwise, x must be a numeric data vector, and g must be a vector or factor object of the same length as x giving the group for the corresponding elements of x.

Hartley's parametric test requires normality and a nearly balanced design. The p-value of the test is calculated with the function pmaxFratio

of the package SuppDists.

Examples

hartleyTest(count ~ spray, data = InsectSprays)

References

Hartley, H.O. (1950) The maximum F-ratio as a short cut test for heterogeneity of variance, Biometrika 37 , 308--312.

See Also

bartlett.test, pmaxFratio