Figure 4

Analytical and biological heteroscedasticity in the data. A: Analytical standard deviation (experiment G1), B: Biological standard deviation (all glucose experiments), and C: Relative biological standard deviation (all glucose experiments), as a function of the metabolite concentration. To obtain a clearer overview, the standard deviations were grouped together based on average mean value of the peak area (Binning, see Jansen et al. [23]). The first bin contained the metabolites whose peak area was below the detection limit.