wilcoxE.test {PASWR}

Wilcoxon Exact Test

Description

Performs exact one sample and two sample Wilcoxon tests on vectors of data

Usage

wilcoxE.test(
  x,
  y = NULL,
  mu = 0,
  paired = FALSE,
  alternative = c("two.sided", "less", "greater"),
  conf.level = 0.95
)

Arguments

x

is a numeric vector of data values. Non-finite (i.e. infinite or missing) values will be omitted.

y

an optional numeric vector of data values

mu

a number specifying an optional parameter used to form the null hypothesis

paired

a logical indicating whether you want a paired test

alternative

a character string specifying the alternative hypothesis, must be one of "two.sided" (default), "less", or "greater". You can specify just the initial letter.

conf.level

confidence level of the interval

Details

If only x is given, or if both x and y are given and paired = TRUE, a Wilcoxon signed rank test of the null hypothesis that the distribution of x (in the one sample case) or of x - y (in the paired two sample case) is symmetric about mu is performed.

Otherwise, if both x and y are given and paired = FALSE, a Wilcoxon rank sum test is done. In this case, the null hypothesis is that the distribution of x and y differ by a location shift mu, and the alternative is that they differ by some other location shift (and the one-sided alternative "greater" is that x is shifted to the right of y).

Value

A list of class htest, containing the following components:

statistic

the value of the test statistic with a name describing it

p.value

the p-value for the test

null.value

the location parameter mu

alternative

a character string describing the alternative hypothesis

method

the type of test applied

data.name

a character string giving the names of the data

conf.int

a confidence interval for the location parameter

estimate

an estimate of the location parameter

Note

The function is rather primitive and should only be used for problems with fewer than 19 observations as the memory requirements are rather large.

Author(s)

Alan T. Arnholt <[e-mail]>

References

• Gibbons, J.D. and Chakraborti, S. 1992. Nonparametric Statistical Inference. Marcel Dekker Inc., New York.

• Hollander, M. and Wolfe, D.A. 1999. Nonparametric Statistical Methods. New York: John Wiley & Sons.

See Also

wilcox.test

Examples

 
# Wilcoxon Signed Rank Test
PH <- c(7.2, 7.3, 7.3, 7.4)
wilcoxE.test(PH, mu = 7.25, alternative = "greater")
# Wilcoxon Signed Rank Test (Dependent Samples)
with(data = Aggression, 
wilcoxE.test(violence, noviolence, paired = TRUE, alternative = "greater"))
# Wilcoxon Rank Sum Test
x <- c(7.2, 7.2, 7.3, 7.3)
y <- c(7.3, 7.3, 7.4, 7.4)
wilcoxE.test(x, y)
rm(PH, x, y)