The reaction is irreproducible in each run due to the initial inhomogeneity of the mixture which result from variation in stirring rate, overall volume as well as geometry of the reactors. Repeating the reaction in the statistically meaningful manners leads to the reproducible cumulative probability distribution curve. The example for this clock is iodate/arsenous acid reaction.
One reaction may fall into more than one classification above depending on the circumstance.  For example, iodate−arsenous acid reaction can be substrate-depletive clock reaction, autocatalysis-driven clock reaction and crazy clock reaction.