mood.test
Mood Two-Sample Test of Scale
Description
Performs Mood's two-sample test for a difference in scale parameters.
Usage
mood.test(x, ...) ## Default S3 method: mood.test(x, y, alternative = c("two.sided", "less", "greater"), ...) ## S3 method for class 'formula' mood.test(formula, data, subset, na.action, ...)
Arguments
x, y | numeric vectors of data values. |
alternative | indicates the alternative hypothesis and must be one of |
formula | a formula of the form |
data | an optional matrix or data frame (or similar: see |
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 |
... | further arguments to be passed to or from methods. |
Details
The underlying model is that the two samples are drawn from f(x-l) and f((x-l)/s)/s, respectively, where l is a common location parameter and s is a scale parameter.
The null hypothesis is s = 1.
There are more useful tests for this problem.
In the case of ties, the formulation of Mielke (1967) is employed.
Value
A list with class "htest"
containing the following components:
statistic | the value of the test statistic. |
p.value | the p-value of the test. |
alternative | a character string describing the alternative hypothesis. You can specify just the initial letter. |
method | the character string |
data.name | a character string giving the names of the data. |
References
William J. Conover (1971), Practical nonparametric statistics. New York: John Wiley & Sons. Pages 234f.
Paul W. Mielke, Jr. (1967). Note on some squared rank tests with existing ties. Technometrics, 9/2, 312–314. doi: 10.2307/1266427.
See Also
fligner.test
for a rank-based (nonparametric) k-sample test for homogeneity of variances; ansari.test
for another rank-based two-sample test for a difference in scale parameters; var.test
and bartlett.test
for parametric tests for the homogeneity in variance.
Examples
## Same data as for the Ansari-Bradley test: ## Serum iron determination using Hyland control sera ramsay <- c(111, 107, 100, 99, 102, 106, 109, 108, 104, 99, 101, 96, 97, 102, 107, 113, 116, 113, 110, 98) jung.parekh <- c(107, 108, 106, 98, 105, 103, 110, 105, 104, 100, 96, 108, 103, 104, 114, 114, 113, 108, 106, 99) mood.test(ramsay, jung.parekh) ## Compare this to ansari.test(ramsay, jung.parekh)
Copyright (©) 1999–2012 R Foundation for Statistical Computing.
Licensed under the GNU General Public License.