oneway.test

From stats v3.2.2 by R-core R-core@R-project.org

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.

Keywords: htest

Usage

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

Arguments

formula: a formula of the form lhs ~ rhs where lhs gives the sample values and rhs 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").
var.equal: 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.

Details

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

Value

statistic: the value of the test statistic.
parameter: the degrees of freedom of the exact or approximate F distribution of the test statistic.
p.value: the p-value of the test.
method: a character string indicating the test performed.
data.name: a character string giving the names of the data.

References

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

Examples

library(stats)

## 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))

Documentation reproduced from package stats, version 3.2.2, License: Part of R 3.2.2

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