  The weak transient detected by the Fermi Gamma-ray Burst Monitor (GBM) 0.4 s
after GW150914 has generated much speculation regarding its possible
association with the black-hole binary merger. Investigation of the GBM data by
Connaughton et al. (2016) revealed a source location consistent with GW150914
and a spectrum consistent with a weak, short Gamma-Ray Burst.
  Greiner et al. (2016) present an alternative technique for fitting
background-limited data in the low-count regime, and call into question the
spectral analysis and the significance of the detection of GW150914-GBM
presented in Connaughton et al. (2016). The spectral analysis of Connaughton et
al. (2016) is not subject to the limitations of the low-count regime noted by
Greiner et al. (2016). We find Greiner et al. (2016) used an inconsistent
source position and did not follow the steps taken in Connaughton et al. (2016)
to mitigate the statistical shortcomings of their software when analyzing this
weak event. We use the approach of Greiner et al. (2016) to verify that our
original spectral analysis is not biased.
  The detection significance of GW150914-GBM is established empirically, with a
False Alarm Rate (FAR) of $\sim 10^{-4}$~Hz. A post-trials False Alarm
Probability (FAP) of $2.2 \times 10^{-3}$ ($2.9 \sigma$) of this transient
being associated with GW150914 is based on the proximity in time to the GW
event of a transient with that FAR. The FAR and the FAP are unaffected by the
spectral analysis that is the focus of Greiner et al. (2016).
