permtest {BHH2} | R Documentation |

## Permutation test: randomization test for small size samples

### Description

Permutation test for means and variance comparisons.

### Usage

```
permtest(x, y = NULL)
```

### Arguments

`x` |
numeric vector. Sample group X. |

`y` |
numeric vector. Sample group Y. |

### Details

In the one–sample problem, the function builds all `2^n`

possible `\pm x_i`

combinations. For the two–sample problem,
all possible `B(n+m,n)`

samples size
`n`

(=`length(x)`

) and `m`

(=`length(y)`

) are
generated and the permutation distributions for the *t*-statistics
and *F*-ratios. *p*-values are computed based on these
distributions.

### Value

The function returns the number `N`

of different samples
generated for the permutation distribution, the observed *t*-statistic,
its *p*-value, based on both, the parametric and permutation
distributions as well as the observed *F*-ratio and its corresponding
*p*-values. The test may take a long time to generate all the possible
combinations. It has been tested for `n + m = 22`

and
`n < 12`

.

### WARNING

The test may take a long time to generate all the possible combinations.

### Author(s)

Ernesto Barrios

### References

Box G. E. P, Hunter, J. S. and Hunter, W. C. (2005).
*Statistics for Experimenters II*. New York: Wiley.

### See Also

`onet.permutation`

and `towt.permutation`

of DAAG package, and `perm.test`

of the exactRankTests.

### Examples

```
library(BHH2)
# Permutation test for Tomato Data
data(tomato.data)
cat("Tomato Data (not paired):\n")
attach(tomato.data)
a <- pounds[fertilizer=="A"]
b <- pounds[fertilizer=="B"]
print(round(test <- permtest(b,a),3))
detach()
# Permutation test for Boy's Shoes Example
data(shoes.data)
cat("Shoes Data (paired):\n")
attach(shoes.data)
x <- matB-matA
print(round(test <- permtest(x),3))
detach()
```

*BHH2*version 2016.05.31 Index]