Fig. 2
From: Response shift in health-related quality of life measures in the presence of formative indicators
Formative model for HRQoL latent variable based on the domain indicators of the EORTC QOL-C30 questionnaire. Note: OH, overall health; QoL, overall quality of life; FC, functioning scales; PA, pain; FA, fatigue; γ referring to the contribution (weights) of formative indicators (FA and PA) to the latent variable (HRQOL); ζ represents the error or residual of the latent variable (HRQOL); ε refers to the error term for the reflective indicators (OH, QoL, FC); λ indicates the loading of the reflective indicators (OH, QoL, FC) on the latent variable