of qualified tethers. In (a–e), the dots ; the lines show $\Jrmsfour$. (a) Trajectory associated with an accepted data set (blue) and stuck bead (green). (b) Trajectory for a bead that passed “minimum motion” but failed the “motion symmetry” test (see (e)). (c) Trajectory associated with nonuniform motion caused by transient, nonspecific binding, seen as a downward spike between 0 and 50 seconds. (d) $xy$ scatter plot of the trajectory in (a) shows it to be symmetric. (e) Scatter plot of the motion in (b) shows it to be asymmetric. The DNA used in (a–e) are 1206bp long and the bead size is 490nm in diameter. (f) Distribution of bead excursions and the number of beads that pass successive application of the selection criteria (see text) [@Blumberg2005]. Red: original data. Cyan: after application of minimal motion filter. Blue: after application of symmetry filter. Green: after application of uniformity filter. The DNA used in (f) are 901bp long and bead size is 490nm diameter. ](calibrationfigPN/selectioneff.eps "fig:"){width="3in"} ![\[fig:selection\] Selection of qualified tethers. In (a–e), the dots ; the lines show $\Jrmsfour$. (a) Trajectory associated with an accepted data set (blue) and stuck bead (green). (b) Trajectory for a bead that passed “minimum 