PMCMRplus (version 1.9.3)

steelsKSampleTest: Steel's k-Treatments vs. Control Test

Description

Performs the non-parametric Steel's test for simultaneously testing k-treatments vs. one control.

Usage

steelsKSampleTest(x, ...)
# S3 method for default
steelsKSampleTest(x, g, alternative = c("two.sided", "greater", "less"), ...)
# S3 method for formula
steelsKSampleTest(
  formula,
  data,
  subset,
  na.action,
  alternative = c("two.sided", "greater", "less"),
  ...
)

Arguments

x

a numeric vector of data values, or a list of numeric data vectors.

…

further arguments to be passed to or from methods.

g

a vector or factor object giving the group for the corresponding elements of "x". Ignored with a warning if "x" is a list.

alternative

the alternative hypothesis. Defaults to two.sided.

formula

a formula of the form response ~ group where response gives the data values and group a vector or factor of 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").

Value

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

method

a character string indicating what type of test was performed.

data.name

a character string giving the name(s) of the data.

statistic

the estimated quantile of the test statistic.

p.value

the p-value for the test.

parameter

the parameters of the test statistic, if any.

alternative

a character string describing the alternative hypothesis.

estimates

the estimates, if any.

null.value

the estimate under the null hypothesis, if any.

Details

It tests \(H: F(i) = F(0), ~ i \le k\), against \(A: F(i) > F(0)\) (greater) with at least one inequality being strict.

The function is a wrapper function that calls Steel.test of the package kSamples with argument method = "asymptotic".

References

Scholz, F. and Zhu, A. (2019). kSamples: K-Sample Rank Tests and their Combinations. R package version 1.2-9. https://CRAN.R-project.org/package=kSamples

Steel, R. G. D. (1959) A Multiple Comparison Rank Sum Test: Treatments Versus Control, Biometrics 15, 560--572.

See Also

Steel.test, flignerWolfeTest

Examples

# NOT RUN {
## Example from Sachs (1997, p. 402)
x <- c(106, 114, 116, 127, 145,
110, 125, 143, 148, 151,
136, 139, 149, 160, 174)
g <- gl(3,5)
levels(g) <- c("0", "I", "II")

## Steel's Test
steelsKSampleTest(x ~ g, alternative = "greater")


## Example from USEPA (2002):
## Reproduction data from a Ceriodaphnia dubia
## 7-day chronic test to several concentrations
## of effluent. Dose level 50% is excluded.
x <- c(20, 26, 26, 23, 24, 27, 26, 23, 27, 24,
13, 15, 14, 13, 23, 26, 0, 25, 26, 27,
18, 22, 13, 13, 23, 22, 20, 22, 23, 22,
14, 22, 20, 23, 20, 23, 25, 24, 25, 21,
9, 0, 9, 7, 6, 10, 12, 14, 9, 13,
rep(0,10))
g <- gl(6, 10)
levels(g) <- c("Control", "3%", "6%", "12%", "25%", "50%")

## NOEC at 3%, LOEC at 6%
steelsKSampleTest(x ~ g, subset = g != "50%", alternative = "less")

# }