| % File src/library/stats/man/oneway.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{oneway.test} |
| \alias{oneway.test} |
| \title{Test for Equal Means in a One-Way Layout} |
| \description{ |
| Test whether two or more samples from normal distributions have the |
| same means. The variances are not necessarily assumed to be equal. |
| } |
| \usage{ |
| oneway.test(formula, data, subset, na.action, var.equal = FALSE) |
| } |
| \arguments{ |
| \item{formula}{a formula of the form \code{lhs ~ rhs} where \code{lhs} |
| gives the sample values and \code{rhs} 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{var.equal}{a logical variable indicating whether to treat the |
| variances in the samples as equal. If \code{TRUE}, then a simple F |
| test for the equality of means in a one-way analysis of variance is |
| performed. If \code{FALSE}, an approximate method of Welch (1951) |
| is used, which generalizes the commonly known 2-sample Welch test to |
| the case of arbitrarily many samples.} |
| } |
| \value{ |
| A list with class \code{"htest"} containing the following components: |
| \item{statistic}{the value of the test statistic.} |
| \item{parameter}{the degrees of freedom of the exact or approximate F |
| distribution of the test statistic.} |
| \item{p.value}{the p-value of the test.} |
| \item{method}{a character string indicating the test performed.} |
| \item{data.name}{a character string giving the names of the data.} |
| } |
| \details{ |
| If the right-hand side of the formula contains more than one term, |
| their interaction is taken to form the grouping. |
| } |
| \references{ |
| B. L. Welch (1951). |
| On the comparison of several mean values: an alternative approach. |
| \emph{Biometrika}, \bold{38}, 330--336. |
| \doi{10.2307/2332579}. |
| } |
| \seealso{ |
| The standard t test (\code{\link{t.test}}) as the special case for two |
| samples; |
| the Kruskal-Wallis test \code{\link{kruskal.test}} for a nonparametric |
| test for equal location parameters in a one-way layout. |
| } |
| \examples{ |
| ## Not assuming equal variances |
| oneway.test(extra ~ group, data = sleep) |
| ## Assuming equal variances |
| oneway.test(extra ~ group, data = sleep, var.equal = TRUE) |
| ## which gives the same result as |
| anova(lm(extra ~ group, data = sleep)) |
| } |
| \keyword{htest} |