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 +/- 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.

Ernesto Barrios

### References

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

`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()

```

[Package BHH2 version 2016.05.31 Index]