WRS2 (version 0.4-0)

yuen: Independent samples t-tests on robust location measures.

Description

The function yuen performs Yuen's test for trimmed means, yuenbt is a bootstrap version of it. The pb2gen function performs a t-test based on various robust estimators.

Usage

yuen(formula, data, tr = 0.2)
yuenbt(formula, data, tr = 0.2, nboot = 599)
pb2gen(formula, data, est = "mom", nboot = 599)

Arguments

formula

an object of class formula.

data

an optional data frame for the input data.

tr

trim level for the mean.

nboot

number of bootstrap samples.

est

Estimate to be used for the group comparisons: either "onestep" for one-step M-estimator of location using Huber's Psi, "mom" for the modified one-step (MOM) estimator of location based on Huber's Psi, or "median", "mean".

Value

Returns objects of classes "yuen" or "pb2" containing:

test

value of the test statistic (t-statistic)

p.value

p-value

conf.int

confidence interval

df

degress of freedom

diff

trimmed mean difference

call

function call

References

Wilcox, R. (2012). Introduction to Robust Estimation and Hypothesis Testing (3rd ed.). Elsevier.

Yuen, K. K. (1974). The two sample trimmed t for unequal population variances. Biometrika, 61, 165-170.

See Also

t1way,t1waybt

Examples

## Yuen's test
yuen(Anxiety ~ Group, data = spider)

## Bootstrap version of Yuen's test (symmetric CIs)
yuenbt(Anxiety ~ Group, data = spider)

## Using an M-estimator
pb2gen(Anxiety ~ Group, data = spider, est = "mom")
pb2gen(Anxiety ~ Group, data = spider, est = "mean")
pb2gen(Anxiety ~ Group, data = spider, est = "median")