  We study the parameter estimation of gravitational waves for aligned-spin
binary black hole (BBH) signals and assess the impact of bias that can be
produced by using nonspinning template waveforms. We employ simple methods to
calculate the statistical uncertainty from an overlap distribution. For the
fiducial waveform model, we use a phenomenological model, which is designed to
generate the gravitational waveforms emitted from merging BBH systems. We show
that the mass parameters recovered by nonspinning waveform templates can be
significantly biased from the true values of aligned-spin signals. By comparing
the systematic bias with the statistical uncertainty, we examine the validity
of nonspinning templates for the parameter estimation of aligned-spin BBHs.
