pois.conf.int {epitools}R Documentation

Confidence intervals for Poisson counts or rates

Description

Calculates confidence intervals for Poisson counts or rates

Usage

pois.exact(x, pt = 1, conf.level = 0.95)
pois.byar(x, pt = 1, conf.level = 0.95)
pois.approx(x, pt = 1, conf.level = 0.95)

Arguments

x count or vector of counts
pt person-time at risk (default = 1) or vector of person-times
conf.level confidence level (default = 0.95)

Details

By default, pois.exact calculates an exact confidence interval for a Poisson count x (pt = 1). To calculate an exact confidence interval for a crude rate (count divided by person-time at risk), set pt equal to the person-time at risk. Both x and pt can be either a number or a vector of numbers.

By default, pois.byar calculates a confidence interval for a Poisson count x (pt = 1) using Byar's formula which approximates the exact method. To calculate a confidence interval for a crude rate (count divided by person-time at risk), set pt equal to the person-time at risk. Both x and pt can be either a number or a vector of numbers (Rothman).

By default, pois.approx calculates an confidence interval for a Poisson count x (pt = 1) using a normal approximation to the Poisson distribution. To calculate a confidence interval for a crude rate (count divided by person-time at risk), set pt equal to the person-time at risk. Both x and pt can be either a number or a vector of numbers.

Value

This function returns a n x 6 matrix with the following colnames:

x Poisson count
pt person-time at risk
rate crude rate = x/pt
conf.level confidence level
lci lower confidence interval limit
uci upper confidence interval limit

Note

Visit http://www.epitools.net for the latest.

Author(s)

Tomas Aragon, aragon@berkeley.edu, http://www.medepi.net/aragon; with contributions by Francis Dimzon fdimzon@yahoo.com

References

Tomas Aragon, et al. Applied Epidemiology Using R. Available at http://www.epitools.net

Kenneth Rothman (2002), Epidemiology: An Introduction, Oxford University Press, 1st Edition.

See Also

binom.conf.int

Examples

pois.exact(1:10)
pois.byar(1:10)
pois.approx(1:10)


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