Fig. 1

Pathways in the measurement model used in the Confirmatory Factor Analysis in phase III studies. Equal weighting of each item (erythema, induration, scaling) is assumed. Ovals represent unobserved (latent) factors (i.e., PGA at baseline and post-baseline); rectangles represent observed items (e.g., erythema, induration, scaling). Loadings from PGA to each item are symbolised by ‘lvf1’ (baseline) and ‘lvf2’ (post-baseline). Residual or error terms represent all factors influencing variability in an item other than the latent factor that precedes and predicts that item. Error terms begin with ‘e’ and end with two digits indicating the item measured (e.g., ‘e11’ = error term for erythema and corresponding variances begin with ‘var’). Covariances between pairs of error terms (latent factors) begin with ‘c’ (e.g., ‘ce11e21’ = covariance of the error term between erythema at baseline and at post-baseline). PGA Physician Global Assessment