Fig. 1

One-factor model for OHRQoL assessed with 14-item OHIP at two occasions; Note: rectangles represent items (i.e., measured or observed variables [OHIP₂ – OHIP₄₈]), ovals reflect latent common factors [OHRQoL₁ and OHRQoL₂], triangles indicate intercepts [τ₂ − τ₄₈ and τ´ ₂ − τ´ ₄₈], unidirectional arrows illustrate directional links (i.e., values of regression parameters for factor loadings [λ₂ − λ₄₈ and λ´ ₂ − λ´ ₄₈] and intercepts), and bidirectional arrows illustrate common factor variances [Φ _1,1 and Φ _2,2] and between-occasion factor covariance [Φ _1,2] as well as item residual variances [ Ω _{2_1,1} − Ω _{48_1,1} and Ω _{2_2,2} − Ω _{48_2,2}] and covariances [Ω _{2_1,2} − Ω _{48_1,2}]. For clarity, notation is slightly different than that used in the text