Observed distribution of coverage of Illumina's Genome Analyzer-2 with a mean coverage over a 4-Mbp region of C. elegans. The distribution best fits a Gamma distribution Γ(α,β) with shape parameters α = 6.3 and . A Poisson distribution is also shown in the figure to compare fits. These results have also been reported by the authors in Sarin et al. (2008).