oneway.test {stats}R Documentation

Test for Equal Means in a One-Way Layout


Test whether two or more samples from normal distributions have the same means. The variances are not necessarily assumed to be equal.


oneway.test(formula, data, subset, na.action, var.equal = FALSE)



a formula of the form lhs ~ rhs where lhs gives the sample values and rhs the corresponding groups.


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).


an optional vector specifying a subset of observations to be used.


a function which indicates what should happen when the data contain NAs. Defaults to getOption("na.action").


a logical variable indicating whether to treat the variances in the samples as equal. If TRUE, then a simple F test for the equality of means in a one-way analysis of variance is performed. If 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.


If the right-hand side of the formula contains more than one term, their interaction is taken to form the grouping.


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


the value of the test statistic.


the degrees of freedom of the exact or approximate F distribution of the test statistic.


the p-value of the test.


a character string indicating the test performed.

a character string giving the names of the data.


B. L. Welch (1951), On the comparison of several mean values: an alternative approach. Biometrika, 38, 330–336.

See Also

The standard t test (t.test) as the special case for two samples; the Kruskal-Wallis test kruskal.test for a nonparametric test for equal location parameters in a one-way layout.


## 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))

[Package stats version 3.3.2 Index]