G.test: G-test
In RVAideMemoire: Testing and Plotting Procedures for Biostatistics

G.test

R Documentation

G-test

Description

Perfoms a G-test on a contingency table or a vector of counts.

Usage

G.test(x, p = rep(1/length(x), length(x)))

Arguments

`x`	a numeric vector or matrix (see Details).
`p`	theoretical proportions (optional).

Details

If x is matrix, it must be constructed like this:

- 2 columns giving number of successes (left) and fails (right)

- 1 row per population.

The function works as chisq.test :

- if x is a vector and theoretical proportions are not given, equality of counts is tested

- if x is a vector and theoretical proportions are given, equality of counts to theoretical counts (given by theoretical proportions) is tested

- if x is a matrix with two columns, equality of proportion of successes between populations is tested.

- if x is a matrix with more than two columns, independence of rows and columns is tested.

Since a G-test is an approximate test, an exact test is preferable when the number of individuals is small (200 is a reasonable minimum). See multinomial.test in that case with a vector, fisher.test with a matrix.

Value

`method`	name of the test.
`statistic`	test statistics.
`parameter`	test degrees of freedom.
`p.value`	p-value.
`data.name`	a character string giving the name(s) of the data.
`observed`	the observed counts.
`expected`	the expected counts under the null hypothesis.