  Common techniques in Gravitational Wave data analysis assume, to some extent,
the stationarity and Gaussianity of the detector noise. These assumptions are
not always satisfied because of the presence of short-duration transients,
namely glitches, and other slower variations in the statistical properties of
the noise, which might be related to malfunctioning subsystems. We present here
a new technique to test the stationarity hypothesis with minimal assumptions on
the data, exploiting the band-limited root mean square and the two-sample
Kolmogorov-Smirnov test. The outcome is a time-frequency map showing where the
hypothesis is to be rejected. This technique was used as part of the event
validation procedure for assessing the quality of the LIGO and Virgo data
during O3. We also report on the applications of the test to both simulated and
real data, highlighting its sensitivity to various kinds of non-stationarities.
