Distributions of the excess significances χ_λ for the 94 DEBRIS M-type dwarfs observed with Herschel/PACS at λ=100 and 160 µm. The Gaussians shown in red are computed with σ = 1 and normalized with the total number of stars excluding the two detections to serve as a guide to characterize the observed noise distribution which is found to be well centered on zero. The excesses of the two disks GJ581 (χ₁₀₀ = 12.1 and χ₁₆₀ = 4.2) and Fom C (χ₁₀₀ = 3.2 and χ₁₆₀ = 7.2) at 100 and 160 µm are apparent in the plots.