| % File src/library/stats/man/mood.test.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2018 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{mood.test} |
| \alias{mood.test} |
| \alias{mood.test.default} |
| \alias{mood.test.formula} |
| \title{Mood Two-Sample Test of Scale} |
| \description{ |
| Performs Mood's two-sample test for a difference in scale parameters. |
| } |
| \usage{ |
| mood.test(x, \dots) |
| |
| \method{mood.test}{default}(x, y, |
| alternative = c("two.sided", "less", "greater"), \dots) |
| |
| \method{mood.test}{formula}(formula, data, subset, na.action, \dots) |
| } |
| \arguments{ |
| \item{x, y}{numeric vectors of data values.} |
| \item{alternative}{indicates the alternative hypothesis and must be |
| one of \code{"two.sided"} (default), \code{"greater"} or |
| \code{"less"} all of which can be abbreviated.} |
| \item{formula}{a formula of the form \code{lhs ~ rhs} where \code{lhs} |
| is a numeric variable giving the data values and \code{rhs} a factor |
| with two levels giving the corresponding groups.} |
| \item{data}{an optional matrix or data frame (or similar: see |
| \code{\link{model.frame}}) containing the variables in the |
| formula \code{formula}. By default the variables are taken from |
| \code{environment(formula)}.} |
| \item{subset}{an optional vector specifying a subset of observations |
| to be used.} |
| \item{na.action}{a function which indicates what should happen when |
| the data contain \code{NA}s. Defaults to |
| \code{getOption("na.action")}.} |
| \item{\dots}{further arguments to be passed to or from methods.} |
| } |
| \details{ |
| The underlying model is that the two samples are drawn from |
| \eqn{f(x-l)} and \eqn{f((x-l)/s)/s}, respectively, where \eqn{l} is a |
| common location parameter and \eqn{s} is a scale parameter. |
| |
| The null hypothesis is \eqn{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 \code{"htest"} containing the following components: |
| \item{statistic}{the value of the test statistic.} |
| \item{p.value}{the p-value of the test.} |
| \item{alternative}{a character string describing the alternative |
| hypothesis. You can specify just the initial letter.} |
| \item{method}{the character string \code{"Mood two-sample test of scale"}.} |
| \item{data.name}{a character string giving the names of the data.} |
| } |
| \references{ |
| William J. Conover (1971), |
| \emph{Practical nonparametric statistics}. |
| New York: John Wiley & Sons. |
| Pages 234f. |
| |
| Paul W. Mielke, Jr. (1967). |
| Note on some squared rank tests with existing ties. |
| \emph{Technometrics}, \bold{9}/2, 312--314. |
| \doi{10.2307/1266427}. |
| } |
| \seealso{ |
| \code{\link{fligner.test}} for a rank-based (nonparametric) k-sample |
| test for homogeneity of variances; |
| \code{\link{ansari.test}} for another rank-based two-sample test for a |
| difference in scale parameters; |
| \code{\link{var.test}} and \code{\link{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) |
| } |
| \keyword{htest} |