Fig. 4

Trend scale and perturbation simulation. a Probability density functions used to simulate maximum compound concentration distributions. b A comparison of observed (darker grey) and simulated (lighter grey) maximum compound concentration distributions (with a semi-transparent overlap). c Probability density functions used to simulate fraction concentration change distribution. d A comparison of observed (darker grey) and simulated (lighter grey) fraction concentration change distributions (with a semi-transparent overlap). e Probability density functions used to simulate fraction relative standard deviation distribution. f A comparison of observed (darker grey) and simulated (lighter grey) relative standard deviation. The curves represent kernel density estimates, with the simulated data generated from 10000 samples per classification from mixtures of two normal distributions (see text for details). Observed data points are shown below the curves