mdd.satterthwaite {MDD}R Documentation

MDD for Student's t-Test (Unequal Variances)

Description

Calculates minimum detectable difference for a two-sample t-test with unequal variances using Satterthwaite's approximation to the degrees of freedom.

Usage

mdd.satterthwaite(n1, n2, mu1, sigma1, sigma2, alpha = 0.05, alternative = "two.sided", 
                  return.cis = FALSE)

Arguments

n1,n2 number of subjects in each sample.
mu1 anticipated mean in sample 1 (control).
sigma1,sigma2 assumed standard deviations in each sample.
alpha significance level.
alternative indicates the alternative hypothesis and must be one of "two.sided", "greater", or "less". You can specify just the initial letter.
return.cis a logical which indicates whether to return endpoints of confidence intervals or just the MDD.

Details

alternative = "less" is the alternative that has the treatment group mean less than the control group mean.

Value

If return.cis = FALSE, the returned value is the MDD.
If return.cis = TRUE, the returned value is a numeric vector of length two giving the closest values to mu1 that would be significant given the remaining parameters.

Note

For equal variances, use mdd.t.test

Author(s)

Don Barkauskas (barkda@wald.ucdavis.edu)

See Also

gui.mdd for a GUI version

Examples

mdd.satterthwaite(20, 15, 3.1, .25, .5)
mdd.satterthwaite(20, 15, 3.1, .25, .5, return.cis=TRUE)

[Package MDD version 0.5 Index]