t.and.smd.conversion {MBESS}

Conversion functions for noncentral t-distribution

Description

Functions useful for converting a standardized mean difference to a noncentrality parameter, and vice versa.

Usage

lambda2delta(lambda, n.1, n.2)
delta2lambda(delta, n.1, n.2)

Arguments

lambda

noncentral value from a t-distribution

delta

population value of the standardized mean difference

n.1

sample size in group 1

n.2

sample size in group 2

Details

Although lambda is the population noncentral value, an estimate of it is the observed value of a t-statistic. Likewise, delta can be estimated as the observed standardized mean difference. Thus, the observed standardized mean difference can be converted to the observed t-value. These functions are especially helpful in the context of forming confidence intervals for the population standardized mean difference.

Value

Either the value of delta given lambda or lambda given delta (and the per group sample sizes).

Author(s)

Ken Kelley (University of Notre Dame; [e-mail])

See Also

smd, ci.smd, ss.aipe.smd

Examples

lambda2delta(lambda=2, n.1=113, n.2=113)
delta2lambda(delta=.266076, n.1=113, n.2=113)