# power.anova.test

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

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

- Keywords
- htest

##### 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.

##### See Also

##### Examples

`library(stats)`

```
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
```

*Documentation reproduced from package stats, version 3.3.3, License: Part of R 3.3.3*

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