Top: mass ratio q = m_A/m_B for each of the binaries including error bars. The fractional error of the secondary is generally similar to that of the primary, and consequently the absolute error for the secondary is invisibly small on this plot for small m_B. Red dashed lines correspond to mass ratios of 1, 1/2, 1/3, 1/5 and 1/10. Middle: histogram of the secondary mass. Bottom: histogram of the mass ratio.