Figure 2: T-statistic distribution of regression of M-value on age vs. mean M-value of corresponding CpG site for 26,428 DNA methylation markers. Red vertical lines at -2 and 2 represent delineation of unmethylated and methylated levels of CpG sites, such that sites having mean M-value <-2 are considered unmethylated, and sites having mean M-value >2 are methylated.