There are various non-statistical tools that have been typically developed by lean companies, notably by Toyota for minimizing variability in production, such as standardization, introduction of takt time, synchronization, shortening the total production lead time which I am fond of referring to as non statistical tools.
Masaaki ImaiIt is impossible to improve any process until it is standardized. If the process is shifting from here to there, then any improvement will just be one more variation that is occasionally used and mostly ignored. One must standardize, and thus stabilize the process, before continuous improvement can be made.
Masaaki Imai