# CV2se: Helper functions In PowerTOST: Power and Sample Size for (Bio)Equivalence Studies

## Description

Calculates the standard error or the mean squared error from a given CV and vice versa for log-normal data.

## Usage

 ```1 2 3 4``` ```CV2se(CV) se2CV(se) CV2mse(CV) mse2CV(mse) ```

## Arguments

 `CV` coefficient of variatio as ratio (not percent) `se` standard error `mse` mean squared error (aka residual variance)

## Value

Returns
` se = sqrt(log(CV^2+1))`
` CV = sqrt(exp(se^2)-1)`
` mse = log(CV^2+1)`
` CV = sqrt(exp(mse)-1)`

## Note

These functions were originally intended for internal use only but may be useful for others.

D. Labes

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10``` ```# these functions are one liners: CV2se <- function(CV) return(sqrt(log(1.0 + CV^2))) se2CV <- function(se) return(sqrt(exp(se^2)-1)) CV2se(0.3) # should give: # [1] 0.2935604 se2CV(0.2935604) # [1] 0.3 ```

### Example output

```[1] 0.2935604
[1] 0.3
```

PowerTOST documentation built on Jan. 18, 2021, 5:07 p.m.