| chisq.test {base} | R Documentation |
chisq.test performs chi-square tests on contingency tables.
If x is a matrix with one row or column, or if x is a
vector and y is not given, x is treated as a
one-dimensional contingency table. In this case, the hypothesis
tested is whether the population probabilities equal those in
p, or are all equal if p is not given.
If x is a matrix with at least two rows and columns, it is
taken as a two-dimensional contingency table, and hence its entries
should be nonnegative integers. Otherwise, x and y must
be vectors or factors of the same length; incomplete cases are
removed, the objects are coerced into factor objects, and the
contingency table is computed from these. Then, Pearson's chi-square
test of the null that the joint distribution of the cell counts in a
2-dimensional contigency table is the product of the row and column
marginals is performed. Continuity correction is only used in the
2-by-2 case if correct is TRUE.
chisq.test(x, y = NULL, correct = TRUE,
p = rep(1/length(x), length(x)))
x |
a vector or matrix. |
y |
a vector; ignored if |
correct |
a logical indicating whether to apply continuity correction when computing the test statistic. |
A list with class "htest" containing the following components:
statistic |
the value the chi-square test statistic. |
parameter |
the degrees of freedom of the approximate chi-square distribution of the test statistic. |
p.value |
the p-value for the test. |
method |
a character string indicating the type of test performed, and whether continuity correction was used. |
data.name |
a character string giving the name(s) of the data. |
observed |
the observed counts. |
expected |
the expected counts under the null hypothesis. |
data(insects) # Not really a good example
chisq.test(insects$count > 7, insects$spray)
# Prints test summary
chisq.test(insects$count > 7, insects$spray)$obs
# Counts observed
chisq.test(insects$count > 7, insects$spray)$obs
# Counts expected under the null