t_testAB: Student's t test with a preliminary testing for the...

In dusadrian/statistics: Miscellanea Functions For an Intro Stats Class

Student's t test with a preliminary testing for the homogeneity of variances

Description

This function executes the t test for one or two groups. In case of two independent groups, the function verifies if the group variances are equal, using the Ansari-Bradley test.

Usage

t_testAB(x, y = NULL,
         alternative = c("two.sided", "less", "greater"), var.equal = FALSE,
         mu = 0, paired = FALSE, conf.level = 0.95, data)

Arguments

x	A numeric vector.
y	An optional numeric vector, corresponding to the second group.
alternative	Character, for the alternative hypothesis. See details below.
var.equal	Logical argument indicating whether to treat the two variances as being equal
mu	A number indicating the true value of the mean (or difference in means if performing a two sample test).
paired	Logical indicating whether to perform a paired t-test.
conf.level	Confidence level of the interval
data	An optional matrix or a set of data containing the variables from a formula

Details

The argument alternative follows the standard in the base function t.test(), and it can be "two.sided", "less" or "greater". In addition to those options, this function also allows for "!=" and "two.tailed" for the bidirectional alternative hypothesis, as well as "<" and "lower" for the one tailed test on the left tail, and ">" and "higher" for the right tailed test, respectively.

Author(s)

Adrian Dusa

Examples

group1 <- c(13, 14,  9, 12,  8, 10,  5, 10,  9, 12, 16)
group2 <- c(16, 18, 11, 19, 14, 17, 13, 16, 17, 18, 22, 12)

t_testAB(group1, group2)


# or, if the variables are inside a dataset
dataset <- data.frame(
  values = c(group1, group2),
  group = c(rep(1,11), rep(2,12))
)

t_testAB(values ~ group, data = dataset)

dusadrian/statistics documentation built on Jan. 26, 2023, 11:55 p.m.