  Methods for parameter estimation of gravitational-wave data assume that
detector noise is stationary and Gaussian. Real data deviates from these
assumptions, which causes bias in the inferred parameters and incorrect
estimates of the errors. We develop a sensitive test of non-Gaussianity for
real gravitational-wave data which measures meaningful parameters that can be
used to characterize these effects. As a test case, we investigate the quality
of data cleaning performed by the LIGO-Virgo-KAGRA collaboration around
GW200129, a binary black hole signal which overlapped with the noise produced
by the radio frequency modulation. We demonstrate that a significant portion of
the non-Gaussian noise is removed below 50 Hz, yet some of the noise still
remains after the cleaning; at frequencies above 85 Hz, there is no excess
noise removed. We also show that this method can quantify the amount of
non-Gaussian noise in continuous data, which is useful for general detector
noise investigations. To do that, we estimate the difference in non-Gaussian
noise in the presence and absence of light scattering noise.
