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Friedman Rank Sum Test

Usage

friedman.test(y, groups, blocks)

Arguments

y either a numeric vector of data values, or a data matrix.
groups a vector giving the group for the corresponding elements of y if this is a vector; ignored if y is a matrix. If not a factor object, it is coerced to one.
blocks a vector giving the block for the corresponding elements of y if this is a vector; ignored if y is a matrix. If not a factor object, it is coerced to one.

Description

friedman.test can be used for analyzing unreplicated complete block designs (i.e., there is exactly one observation in y for each combination of levels of groups and blocks) where the normality assumption may be violated.

The null hypothesis is that apart from an effect of blocks, the location parameter of y is the same in each of the groups.

If y is a matrix, groups and blocks are obtained from the column and row indices, respectively. NA's are not allowed in groups or blocks; if y contains NA's, corresponding blocks are removed.

Value

A list with class "htest" containing the following components:
statistic the value of Friedman's chi-square statistic.
parameter the degrees of freedom of the approximate chi-square distribution of the test statistic.
p.value the p-value of the test.
method the string "Friedman rank sum test".
data.name a character string giving the names of the data.