The MANCOVA result on the reference θ power shows that the group effect is still significant (F(5,89) = 4.527; p = .001) after removing variance of the P3b amplitude, but the size of the effect is reduced from 14.9% to 11.8%. For the relative θ power MANCOVA, the group effect is also still significant (F(5,89) = 4.906; p = .001) after removing variance of the P3b amplitude, but in this case the size of the effect is not reduced, going from 20.1% to 21.6%. Furthermore, after removing the variance of the reference θ power at MESOIs and the P3b amplitude, the group effect is still significant (F(5,84) = 3.002; p = .015), but the effect size is smaller, going from 21.6% to 15.2%. The trends for the overall MANOVA (MANCOVA) are also observed in the post-hoc univariate ANOVA (ANCOVA) results at MESOIs shown in Table 2.
