Distribution of the 83 Bone and 121 Muscle markers (= training set members) in the population of 34,130 profiles ranked according to the χ² statistic. A rank R of 1 denotes the most variable (significant) profile, a rank of 34,130 the least variable (least significant) profile. N is the cumulative number of markers found with rank below or equal to the rank R indicated on the abcissa. C denotes the profile concentration (see text and equation 3, in Methods) and P_ks is the companion P value (Kolmogorov-Smirnov test). The straight lines indicate the distributions expected if markers were sampled at random in the global population. (a) Bone markers; (b) Muscle markers.