# power.anova.test: Power Calculations for Balanced One-Way Analysis of Variance...

## Description

Compute power of test or determine parameters to obtain target power.

## Usage

 ```1 2 3``` ```power.anova.test(groups = NULL, n = NULL, between.var = NULL, within.var = NULL, sig.level = 0.05, power = NULL) ```

## Arguments

 `groups` Number of groups `n` Number of observations (per group) `between.var` Between group variance `within.var` Within group variance `sig.level` Significance level (Type I error probability) `power` Power of test (1 minus Type II error probability)

## Details

Exactly one of the parameters `groups`, `n`, `between.var`, `power`, `within.var`, and `sig.level` must be passed as NULL, and that parameter is determined from the others. Notice that `sig.level` has non-NULL default so NULL must be explicitly passed if you want it computed.

## Value

Object of class `"power.htest"`, a list of the arguments (including the computed one) augmented with `method` and `note` elements.

## Note

`uniroot` is used to solve power equation for unknowns, so you may see errors from it, notably about inability to bracket the root when invalid arguments are given.

## Author(s)

Claus Ekstrøm

`anova`, `lm`, `uniroot`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12``` ```power.anova.test(groups = 4, n = 5, between.var = 1, within.var = 3) # Power = 0.3535594 power.anova.test(groups = 4, between.var = 1, within.var = 3, power = .80) # n = 11.92613 ## Assume we have prior knowledge of the group means: groupmeans <- c(120, 130, 140, 150) power.anova.test(groups = length(groupmeans), between.var = var(groupmeans), within.var = 500, power = .90) # n = 15.18834 ```