The distribution of the birth-years of 19 founders of statistical sciences, as reported in a recent book on the history of statistics, shows a cirsaseptennian (approximately 7-year) periodicity. A second sample of 31 statistical pioneers, extracted from the Encyclopedia of Statistical Sciences, supports the first observation. Up to the end of the 19th century, founders of statistical sciences tended to be born in years belonging to the 7n+2 phase. There are also indications for circaseptennian patterns connecting different statistical schools during the last century. These findings extend earlier reports of a circaseptennian pattern in the birth-year distribution of physicists.