Permutation test of 22 GHz water maser long-term time series taken with HartRAO. Top panel: Example time series of the −7.32 km s⁻¹ velocity time series. The pre-burst and burst time windows are annotated. Second panel: Distribution of t_stat for 10⁴ iterations where the array is shuffled for the −7.32 km s⁻¹ time series. The value of the unshuffled time series is shown as the black line. Third panel: Value of the ratio of the unshuffled t_stat over the standard deviation of the shuffled distribution. The velocity channels that have a statistically significant increased and decreased dispersion are shown in blue and red, respectively. Bottom panel: Dispersion ratio for channels where there were statistically significant changes. The blue points are σ_burst/σ_pre where the dispersion increased, while the red points are σ_pre/σ_burst where the dispersion decreased.