  In Ref. [1], the properties of the first gravitational wave detected by LIGO,
GW150914, were measured by employing an effective-one-body (EOB) model of
precessing binary black holes whose underlying dynamics and waveforms were
calibrated to numerical-relativity (NR) simulations. Here, we perform the first
extensive comparison of such EOBNR model to 70 precessing NR waveforms that
span mass ratios from 1 to 5, dimensionless spin magnitudes up to 0.5, generic
spin orientations, and length of about 20 orbits. We work in the observer's
inertial frame and include all $\ell=2$ modes in the gravitational-wave
polarizations. We introduce new prescriptions for the EOB ringdown signal
concerning its spectrum and time of onset. For total masses between 10Msun and
200Msun, we find that precessing EOBNR waveforms have unfaithfulness within
about 3% to NR waveforms when considering the Advanced-LIGO design noise curve.
This result is obtained without recalibration of the inspiral-plunge of the
underlying nonprecessing EOBNR model. The unfaithfulness is computed with
maximization over time and phase of arrival, sky location and polarization of
the EOBNR waveform and it is averaged over sky location and polarization of the
NR signal. We also present comparisons between NR and EOBNR waveforms in a
frame that tracks the orbital precession.
