t.and.smd.conversion {MBESS} | R Documentation |
Functions useful for converting a standardized mean difference to a noncentrality parameter, and vise versa.
lambda2delta(lambda, n.1, n.2) delta2lambda(delta, n.1, n.2)
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 |
Although lambda
is the population noncentral value, it can be regarded as the observed value of a
t
-statistics. Likewise, delta can be regarded 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 around the population standardized mean difference.
Either the value of delta given lambda or lambda
given delta
(and the per-group sample sizes).
Ken Kelley (University of Notre Dame; KKelley@ND.Edu)
smd
, ci.smd
, ss.aipe.smd
# lambda2delta(lambda=2, n.1=113, n.2=113) # delta2lambda(delta=.266076, n.1=113, n.2=113)