Confidence interval for Poisson counts.

Source: R/CIDists.R

Computes a confidence interval for the Poisson counts.

poiCI(
  x,
  conf.level = 0.95,
  type = c("exact", "daly", "byar", "asymptotic"),
  verbose = FALSE
)

Arguments

x

A single number or vector that represents the number of observed successes.
conf.level

A number that indicates the level of confidence to use for constructing confidence intervals (default is 0.95).
type

A string that identifies the type of method to use for the calculations. See details.
verbose

A logical that indicates whether x should be included in the returned matrix (=TRUE) or not (=FALSE; DEFAULT).

Value

A #x2 matrix that contains the lower and upper confidence interval bounds as columns and, if verbose=TRUE x.

Details

Computes a CI for the Poisson counts using the exact, gamma distribution (daly`), Byar's (byar), or normal approximation (asymptotic) methods.

The pois.daly function gives essentially identical answers to the pois.exact function except when x=0. When x=0, for the upper confidence limit pois.exact returns 3.689 and pois.daly returns 2.996.

Author

Derek H. Ogle, derek@derekogle.com, though this is largely based on pois.exact, pois.daly, pois.byar, and pois.approx from the old epitools package.

Examples

## Demonstrates using all types at once
poiCI(12)

#>             95% LCI  95% UCI
#> Exact      6.200603 20.96156
#> Daly       6.200575 20.96159
#> Byar       6.552977 20.32447
#> Asymptotic 5.210486 18.78951

## Selecting types
poiCI(12,type="daly")

#>   95% LCI  95% UCI
#>  6.200575 20.96159
poiCI(12,type="byar")

#>   95% LCI  95% UCI
#>  6.552977 20.32447
poiCI(12,type="asymptotic")

#>   95% LCI  95% UCI
#>  5.210486 18.78951
poiCI(12,type="asymptotic",verbose=TRUE)

#>             x  95% LCI  95% UCI
#> Asymptotic 12 5.210486 18.78951
poiCI(12,type=c("exact","daly"))

#>        95% LCI  95% UCI
#> Exact 6.200603 20.96156
#> Daly  6.200575 20.96159
poiCI(12,type=c("exact","daly"),verbose=TRUE)

#>        x  95% LCI  95% UCI
#> Exact 12 6.200603 20.96156
#> Daly  12 6.200575 20.96159

## Demonstrates use with multiple inputs
poiCI(c(7,10),type="exact")

#>   95% LCI  95% UCI
#>  2.814358 14.42268
#>  4.795389 18.39036
poiCI(c(7,10),type="exact",verbose=TRUE)

#>       x  95% LCI  95% UCI
#> [1,]  7 2.814358 14.42268
#> [2,] 10 4.795389 18.39036