Student-Newman-Keuls Test
Performs Student-Newman-Keuls all-pairs comparisons test for normally distributed data with equal group variances.
snkTest(x, ...) ## Default S3 method: snkTest(x, g, ...) ## S3 method for class 'formula' snkTest(formula, data, subset, na.action, ...) ## S3 method for class 'aov' snkTest(x, ...)
x |
a numeric vector of data values, a list of numeric data vectors or a fitted model object, usually an aov fit. |
... |
further arguments to be passed to or from methods. |
g |
a vector or factor object giving the group for the
corresponding elements of |
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 |
For all-pairs comparisons in an one-factorial layout with normally distributed residuals and equal variances Student-Newman-Keuls test can be performed. A total of m = k(k-1)/2 hypotheses can be tested. The null hypothesis H_{ij}: μ_i(x) = μ_j(x) is tested in the two-tailed test against the alternative A_{ij}: μ_i(x) \ne μ_j(x), ~~ i \ne j.
The p-values are computed from the Tukey-distribution.
A list with class "PMCMR"
containing the following components:
a character string indicating what type of test was performed.
a character string giving the name(s) of the data.
lower-triangle matrix of the estimated quantiles of the pairwise test statistics.
lower-triangle matrix of the p-values for the pairwise tests.
a character string describing the alternative hypothesis.
a character string describing the method for p-value adjustment.
a data frame of the input data.
a string that denotes the test distribution.
Keuls, M. (1952) The use of the "studentized range" in connection with an analysis of variance, Euphytica 1, 112–122.
Newman, D. (1939) The distribution of range in samples from a normal population, expressed in terms of an independent estimate of standard deviation, Biometrika 31, 20–30.
Student (1927) Errors of routine analysis, Biometrika 19, 151–164.
fit <- aov(weight ~ feed, chickwts) shapiro.test(residuals(fit)) bartlett.test(weight ~ feed, chickwts) anova(fit) ## also works with fitted objects of class aov res <- snkTest(fit) summary(res) summaryGroup(res)
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