Table 3.

Comparison of the required parameters and the results obtained using the linear regression model and the Raschpower method on the NHP data

Variables	Linear regression model	Raschpower method
σ2	3.9323	3.9323
J	8	8
γ	/	0.649
Ng	/	197
δ	/	(2.61, 2.94, 1.75, 0.46, −0.11, 0.36, 1.28, 2.23)
Ra	1.27210	1.34
NR	251	264

σ²: variance of the latent trait; J: number of items; γ: difference between the mean values of the latent trait in the two groups (group effect); N_g: sample size per group providing a 1-β = 90% power with the classical formula and a 1-β_R = 80% power with Raschpower; δ: vector of the items parameters (δ₁, δ₂, δ₃, δ₄, δ₅, δ₆, δ₇, δ₈); Ra: ratio, N_R: sample size per group providing a 1-β ≈ 90% power for Rasch analysis with the linear regression model and Raschpower, /: not required.