# mudiff.freq: Frequentist sample size determination for differences in... In SampleSizeMeans: Sample size calculations for normal means

## Description

The function `mudiff.freq` returns the required sample sizes to get a confidence interval of given length and confidence level for the difference between two normal means.

## Usage

 `1` ```mudiff.freq(len, lambda1, lambda2, level = 0.95, equal=TRUE) ```

## Arguments

`len`

The desired total length of the confidence interval for the difference between the two unknown means

`lambda1`

Known precision (reciprocal of the variance) for the first population

`lambda2`

Known precision (reciprocal of the variance) for the second population

`level`

The desired confidence level (e.g., 0.95)

`equal`

logical. Whether or not the final group sizes (n1, n2) are forced to be equal:

 when equal = TRUE, final sample sizes n1 = n2; when equal = FALSE, final sample sizes (n1, n2) minimize the variance given a total of n1+n2 observations

## Details

Assume that a random sample from each of two populations will be collected in order to estimate the difference between two independent normal means. Assume further that the two precisions lambda1 and lambda2 are known (where precision is the reciprocal of the variance). The function `mudiff.freq` returns the required sample sizes to attain the desired length len and confidence level level for the confidence interval for the difference between the two unknown means from a frequentist point of view.

## Value

The required sample sizes (n1, n2) for each group given the inputs to the function.

## Note

The sample sizes returned by this function are exact.

## Author(s)

Lawrence Joseph lawrence.joseph@mcgill.ca and Patrick Belisle

## References

Joseph L, Belisle P.
Bayesian sample size determination for Normal means and differences between Normal means
The Statistician 1997;46(2):209-226.

`mudiff.acc`, `mudiff.alc`, `mudiff.modwoc`, `mudiff.acc.equalvar`, `mudiff.alc.equalvar`, `mudiff.modwoc.equalvar`, `mudiff.varknown`, `mudiff.mblacc`, `mudiff.mblalc`, `mudiff.mblmodwoc`, `mudiff.mblacc.equalvar`, `mudiff.mblalc.equalvar`, `mudiff.mblmodwoc.equalvar`, `mudiff.mbl.varknown`, `mu.freq`, `mu.acc`, `mu.alc`, `mu.modwoc`, `mu.varknown`, `mu.mblacc`, `mu.mblalc`, `mu.mblmodwoc`, `mu.mbl.varknown`

## Examples

 ```1 2``` ```# Suppose variance1 = 2, variance2 = 4 mudiff.freq(len=0.2, lambda1=1/2, lambda2=1/4) ```

### Example output

```[1] 2305 2305
```

SampleSizeMeans documentation built on May 1, 2019, 6:50 p.m.