MeanCIn {DescTools} | R Documentation |

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

### Description

Returns the required sample size to obtain a given width of a confidence interval for the sample mean. The function uses `uniroot()`

to find a numeric solution. The t distribution is used.

### Usage

```
MeanCIn(ci, sd, interval = c(2, 100000), conf.level = 0.95,
norm = FALSE, tol = .Machine$double.eps^0.5)
```

### Arguments

`ci` |
the left and right bound of the interval, which is presumed to be symmetric. |

`sd` |
the standard deviation of the sample. |

`interval` |
the interval for the sample size to be searched into, (default is c(2, 100000)). |

`conf.level` |
confidence level, defaults to |

`norm` |
logical, determining if the t- or normaldistribution should be used. |

`tol` |
the desired accuracy (convergence tolerance). |

### Details

The required sample sizes for a specific width of confidence interval for the mean depends recursively on the sample size, as the samplesize defines the degrees of freedom in the t-distribution. Although in most practical cases it will be sufficient to use the normal distribution, we might be interested in exact results.

### Value

a numeric value

### Author(s)

Andri Signorell <andri@signorell.net>

### See Also

`BinomCIn()`

### Examples

```
MeanCIn(ci=c(25, 27), sd=5)
```

*DescTools*version 0.99.54 Index]