power.anova.test {stats} R Documentation

## Power Calculations for Balanced One-Way Analysis of Variance Tests

### Description

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

### Usage

```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`

### Examples

```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
```

[Package stats version 4.1.1 Index]