Estimation of stratum corneum thickness (H) by the linear model (panel a) and by the simple (S-NL) and baseline corrected (BC-NL) non-linear models (panel b) for subjects 1a and 2b. [■] Experimental data points. Panel a: [–] prediction by LM. Panel b: [–] prediction by BC-NL; […] prediction by S-NL model. The vertical lines mark the value of H estimated by the LM (panel a, solid line), the S-NL (panel b, dotted line), and the BD-NL (panel b, solid line).