Distribution of the multinomial likelihood values calculated for each of the 10⁵ simulated sets of peak times under the assumption of no periodic occurrences, in the case of GRB 211211A, also shown in Fig. 2. The vertical blue line shows the corresponding value for the real data, showing that the no-periodic occurences assumption cannot be rejected. Instead, the vertical red line shows the analogous result for a 211211A-like GRB sharing the same number of peaks and non-stationary profile, but with 75% periodic peaks. The p value is clearly ≪10⁻⁵.