Comparison of Calculated Z-scores and Experimental Flux Ranges. a) For several reactions, the computed Z scores are compared to the resulting measured flux ranges. Z-scores show (color coded) Z-scores for each of the 12 reactions and three glucose labels. FVA indicates the absolute allowable flux ranges for three glucoses ([1-13C], [6-13C], [U-13C]) as well as the range if no 13C data is imposed ('none'). A normalized version of this table is also presented where all flux ranges are divided by the FVA range thus showing the fraction of flux range remaining. This quantity ranges from 0 (range fully specified) to 1 (no additional information). b) A receiver operating characteristic (ROC) curve for the ability of Z-scores to predict confidence interval reduction by different fractions. Z-scores are observed to predict larger interval reductions (e.g. ratio<0.2) with higher specificity and sensitivity than smaller reductions (e.g. ratio<0.8).