prop.test(x, n = NULL, p = NULL, alternative = "two.sided", conf.level = 0.95, correct = TRUE)
x
| a vector of counts of successes or a matrix with 2 columns giving the counts of successes and failures, respectively. |
n
|
a vector of counts of trials; ignored if x is a matrix.
|
p
|
a vector of probabilities of success. The length of p
must be the same as the number of groups specified by x , and
its elements must be greater than 0 and less than 1.
|
alternative
|
indicates the alternative hypothesis and must be
one of "two.sided" , "greater" or "less" . You
can specify just the initial letter. Only used for testing the null
that a single proportion equals a given value, or that two
proportions are equal; ignored otherwise.
|
conf.level
| confidence level of the returned confidence interval. Must be a single number between 0 and 1. Only used when testing the null that a single proportion equals a given value, or that two proportions are equal; ignored otherwise. |
correct
| a logical indicating whether Yates' continuity correction should be applied. |
prop.test
can be used for testing the null that the proportions
(probabilities of success) in several groups are the same, or that
they equal certain given values.
Only groups with finite numbers of successes and failures are used. Counts of successes and failures must be nonnegative and hence not greater than the corresponding numbers of trials which must be positive. All finite counts should be integers.
If p
is NULL
and there is more than one group, the null
tested is that the proportions in each group are the same. If there
are two groups, the alternatives are that the probability of success
in the first group is less than, not equal to, or greater than the
probability of success in the second group, as specified by
alternative
. A confidence interval for the difference of
proportions with confidence level as specified by conf.level
and clipped to [-1,1] is returned. Continuity correction is
used only if it does not exceed the difference of the sample
proportions in absolute value. Otherwise, if there are more than 2
groups, the alternative is always "two.sided"
, the returned
confidence interval is NULL
, and continuity correction is never
used.
If there is only one group, then the null tested is that the
underlying probability of success is p
, or .5 if p
is
not given. The alternative is that the probability of success if less
than, not equal to, or greater than p
or 0.5, respectively, as
specified by alternative
. A confidence interval for the
underlying proportion with confidence level as specified by
conf.level
and clipped to [0,1] is returned. Continuity
correction is used only if it does not exceed the difference between
sample and null proportions in absolute value.
Finally, if p
is given and there are more than 2 groups, the
null tested is that the underlying probabilities of success are those
given by p
. The alternative is always "two.sided"
, the
returned confidence interval is NULL
, and continuity correction
is never used.
"htest"
containing the following components:
statistic
| the value of Pearson's chi-square test statistic. |
parameter
| the degrees of freedom of the approximate chi-square distribution of the test statistic. |
p.value
| the p-value of the test. |
estimate
|
a vector with the sample proportions x/n .
|
conf.int
|
a confidence interval for the true proportion if there
is one group, or for the difference in proportions if there are 2
groups and p is not given, or NULL otherwise. In the
cases where it is not NULL , the returned confidence interval
has an asymptotic confidence level as specified by
conf.level , and is appropriate to the specified alternative
hypothesis.
|
null.value
|
the value of p if specified by the null, or
NULL otherwise.
|
alternative
| a character string describing the alternative. |
method
| a character string indicating the method used, and whether Yates' continuity correction was applied. |
data.name
| a character string giving the names of the data. |
heads <- rbinom(1, size=100, pr = .5) prop.test(heads, 100)# continuity correction: Here TRUE by default prop.test(heads, 100, correct = FALSE) ## Data from Fleiss (1981), p. 139. ## H0: The null hypothesis is that the four populations from which ## the patients were drawn have the same true proportion of smokers. ## A: The alternative is that this proportion is different in at ## least one of the populations. smokers <- c( 83, 90, 129, 70 ) patients <- c( 86, 93, 136, 82 ) prop.test(smokers, patients)