Application of the test of Eddington & Plakidis (1929) to the 84 reconstructed cycles on the basis of the ¹⁴C data. Shown is the mean accumulated phase error after x cycles as a function of x. The red curve results from the activity minima of the reconstructed cycles, the blue curve is the corresponding fit to the theoretical relation given by Eq. (23) for x ≤ 50. The resulting fit parameters clearly indicate that the system shows random walk of phase.