| % File src/library/stats/man/poisson.test.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2011 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{poisson.test} |
| \alias{poisson.test} |
| \title{Exact Poisson tests} |
| \description{ |
| Performs an exact test of a simple null hypothesis about the |
| rate parameter in Poisson distribution, or for the |
| ratio between two rate parameters. |
| } |
| \usage{ |
| poisson.test(x, T = 1, r = 1, |
| alternative = c("two.sided", "less", "greater"), |
| conf.level = 0.95) |
| } |
| \arguments{ |
| \item{x}{number of events. A vector of length one or two.} |
| \item{T}{time base for event count. A vector of length one or two. } |
| \item{r}{hypothesized rate or rate ratio} |
| \item{alternative}{indicates the alternative hypothesis and must be |
| one of \code{"two.sided"}, \code{"greater"} or \code{"less"}. |
| You can specify just the initial letter.} |
| \item{conf.level}{confidence level for the returned confidence |
| interval.} |
| } |
| \details{ |
| Confidence intervals are computed similarly to those of |
| \code{\link{binom.test}} in the one-sample case, and using |
| \code{\link{binom.test}} in the two sample case. |
| } |
| \value{ |
| A list with class \code{"htest"} containing the following components: |
| \item{statistic}{the number of events (in the first sample if there |
| are two.)} |
| \item{parameter}{the corresponding expected count} |
| \item{p.value}{the p-value of the test.} |
| \item{conf.int}{a confidence interval for the rate or rate ratio.} |
| \item{estimate}{the estimated rate or rate ratio.} |
| \item{null.value}{the rate or rate ratio under the null, |
| \code{r}.} |
| \item{alternative}{a character string describing the alternative |
| hypothesis.} |
| \item{method}{the character string \code{"Exact Poisson test"} or |
| \code{"Comparison of Poisson rates"} as appropriate.} |
| \item{data.name}{a character string giving the names of the data.} |
| } |
| \note{ |
| The rate parameter in Poisson data is often given based on a |
| \dQuote{time on test} or similar quantity (person-years, population |
| size, or expected number of cases from mortality tables). This is the |
| role of the \code{T} argument. |
| |
| The one-sample case is effectively the binomial test with a very large |
| \code{n}. The two sample case is converted to a binomial test by |
| conditioning on the total event count, and the rate ratio is directly |
| related to the odds in that binomial distribution. |
| } |
| \seealso{ |
| \code{\link{binom.test}} |
| } |
| \examples{ |
| ### These are paraphrased from data sets in the ISwR package |
| |
| ## SMR, Welsh Nickel workers |
| poisson.test(137, 24.19893) |
| |
| ## eba1977, compare Fredericia to other three cities for ages 55-59 |
| poisson.test(c(11, 6+8+7), c(800, 1083+1050+878)) |
| } |
| \keyword{htest} |
| |