The estimate of the noncentrality parameter, λ, obtained by estimating δ and σ by their sample estimates, appears as follows:
The expression on the right illustrates the calculation of the unbiased noncentrality parameter when a sample size N, different from the study size n, is proposed for a retrospective power analysis. Here, dfHyp represents the degrees of freedom for the hypothesis and dfModel represents the degrees of freedom for the whole model.
Poweradj =
Lower CL for λ =
Upper CL for λ =