R: Sample Size for a Given Width of a Binomial Confidence...

BinomCIn {DescTools} | R Documentation

## Sample Size for a Given Width of a Binomial Confidence Interval

### Description

Returns the necessary sample size to achieve a given width of a binomial confidence interval, as calculated by `BinomCI()`. The function uses `uniroot()` to find a numeric solution.

### Usage

    BinomCIn(p = 0.5, width, interval = c(1, 100000),
             conf.level = 0.95, sides = "two.sided", method = "wilson")

### Arguments

`p` | probability for success, defaults to `0.5`.
`width` | the width of the confidence interval
`interval` | a vector containing the end-points of the interval to be searched for the root. The defaults are set to `c(1, 100000)`.
`conf.level` | confidence level, defaults to `0.95`.
`sides` | a character string specifying the side of the confidence interval, must be one of `"two.sided"` (default), `"left"` or `"right"`. You can specify just the initial letter. `"left"` would be analogue to a hypothesis of `"greater"` in a `t.test`.
`method` | character string specifing which method to use; this can be one out of: `"wald"`, `"wilson"`, `"wilsoncc"`, `"agresti-coull"`, `"jeffreys"`, `"modified wilson"`, `"modified jeffreys"`, `"clopper-pearson"`, `"arcsine"`, `"logit"`, `"witting"` or `"pratt"`. Defaults to `"wilson"`. Abbreviation of method are accepted. See details in `BinomCI()`.

### Details

The required sample sizes for a specific width of confidence interval depends on the proportion in the population. This value might be unknown right from the start when a study is planned. In such cases the sample size needed for a given level of accuracy can be estimated using the worst case percentage which is p=50%. When a better estimate is available you can you can use it to get a smaller interval.

### Value

a numeric value

### Author(s)

Andri Signorell <andri@signorell.net>

### See Also

`BinomCI()`

### Examples

    BinomCIn(p=0.1, width=0.05, method="pratt")

[Package DescTools version 0.99.38 Index]