Testing the likelihood that the observed canonical binary-star period distributions fit the K1 IPF (dashed curve) or the DM PDPF (solid line). The model histograms are shown as dotted and solid lines with expected binomial uncertainties as error-bars (Eqs. (7) and (8)). Solid circles are the G-dwarf main-sequence data in the upper panel and canonical pre-main-sequence data in the lower panel (Sect. 2). The χ² value and significance probability, , of observing such a large or larger χ² is written in each panel (upper numbers for testing the data against the K1 IPF, lower numbers for testing against the DM PDPF).