t_test {bain} | R Documentation |
Performs one and two sample t-tests on vectors of data.
t_test(x, ...) ## Default S3 method: t_test(x, y = NULL, alternative = c("two.sided", "less", "greater"), mu = 0, paired = FALSE, var.equal = FALSE, conf.level = 0.95, ...) ## S3 method for class 'formula' t_test(formula, data, subset, na.action, ...)
x |
a (non-empty) numeric vector of data values. |
... |
further arguments to be passed to or from methods. |
y |
an optional (non-empty) numeric vector of data values. |
alternative |
a character string specifying the alternative hypothesis,
must be one of |
mu |
a number indicating the true value of the mean (or difference in means if you are performing a two sample test). |
paired |
a logical indicating whether you want a paired t-test. |
var.equal |
a logical variable indicating whether to treat the two
variances as being equal. If |
conf.level |
confidence level of the interval. |
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 |
The formula interface is only applicable for the 2-sample tests.
alternative = "greater"
is the alternative that x
has a larger
mean than y
.
If paired
is TRUE
then both x
and y
must be
specified and they must be the same length. Missing values are silently
removed (in pairs if paired
is TRUE
). If var.equal
is
TRUE
then the pooled estimate of the variance is used. By default,
if var.equal
is FALSE
then the variance is estimated
separately for both groups and the Welch modification to the degrees of
freedom is used.
If the input data are effectively constant (compared to the larger of the two means) an error is generated.
A list with class "htest"
containing the following
components:
statistic |
the value of the t-statistic. |
parameter |
the degrees of freedom for the t-statistic. |
p.value |
the p-value for the test. |
conf.int |
a confidence interval for the mean appropriate to the specified alternative hypothesis. |
estimate |
the estimated mean or difference in means depending on whether it was a one-sample test or a two-sample test. |
null.value |
the specified hypothesized value of the mean or mean difference depending on whether it was a one-sample test or a two-sample test. |
alternative |
a character string describing the alternative hypothesis. |
method |
a character string indicating what type of t-test was performed. |
data.name |
a character string giving the name(s) of the data. |
In order to allow users to enjoy the functionality of bain with the familiar stats-function t.test, we have had to make minor changes to the function t.test.default. All rights to, and credit for, the function t.test.default belong to the R Core Team, as indicated in the original license below. We make no claims to copyright and incur no liability with regard to the changes implemented in t_test.
This the original copyright notice by the R core team: File src/library/stats/R/t_test.R Part of the R package, https://www.R-project.org
Copyright (C) 1995-2015 The R Core Team
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
A copy of the GNU General Public License is available at https://www.R-project.org/Licenses/
require(graphics) t_test(1:10, y = c(7:20)) # P = .00001855 t_test(1:10, y = c(7:20, 200)) # P = .1245 -- NOT significant anymore ## Classical example: Student's sleep data plot(extra ~ group, data = sleep) ## Traditional interface with(sleep, t_test(extra[group == 1], extra[group == 2])) ## Formula interface t_test(extra ~ group, data = sleep)