Fix standardization of interaction terms: use SD(A)*SD(B)#501
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yrosseel merged 1 commit intoyrosseel:masterfrom Feb 24, 2026
Merged
Fix standardization of interaction terms: use SD(A)*SD(B)#501yrosseel merged 1 commit intoyrosseel:masterfrom
yrosseel merged 1 commit intoyrosseel:masterfrom
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…D(A:B) For interaction terms A:B, standardizedSolution() was using SD(A:B) from the model-implied VETA, which incorrectly forces Var(A:B) = 1. This is only correct when A and Z are orthogonal. The fix replaces ETA[A:B] with SD(A)*SD(B) following Brandt et al. (2015, Eq. 13). Also handles quadratic terms A:A via SD(A)*SD(A) = Var(A). Centering adjustments for non-zero latent means are not yet implemented; a warning is emitted when interaction terms are present.
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Fixes #480 (partially).
For interaction terms A:B,
standardizedSolution()was usingSD(A:B)fromdiag(VETA)to standardize the coefficient. This forcesVar(A:B) = 1, which is only correct when A and B are orthogonal. The correct scaling factor isSD(A)*SD(B)(Brandt et al., 2015, Eq. 13).The fix replaces
ETA[A:B]withSD(A)*SD(B)insidelav_standardize_lv(), which propagates tostd.lv,std.all, andstd.nox. Quadratic termsA:Aare also handled (SD(A)*SD(A) = Var(A)).This does not yet address centering adjustments for models with non-zero latent means — a warning is emitted in that case.