A good definition of a PULL production system

Good definition of a Pull production system.

What Is main Difference between a Push and Pull production system?

A pull production system is one that explicitly limits the amount of work in process that can be in the system. [...] a push production system is one that has no explicit limit on the amount of work in process that can be in the system. (Hopp and Spearman "To Pull or Not to Pull")

A True pull has an upper limit on work in progress, WIP

The Kanban system dictates a fixed upper limit on the work in progress. You cannot have more material than what is allowed by the kanban card ( or signal). The limit is explicitly defined by the kanban card ( or signal )

Selected Source:

Hopp, Wallace J., and Mark L. Spearman. “To Pull or Not to Pull: What Is the Question?” Manufacturing & Service Operations Management 6, No. 2 (April 1, 2004): 133–48. doi:10.1287/msom.1030.0028.

Ronald Fisher and Karl Pearson the Grandfathers of Six Sigma !

Why are Ronald Fisher and Karl Pearson not celebrated and discussed more in Six Sigma forums and in Lean Six Sigma training courses the same way as the likes of Shewhart, Deming and Juran ?  ( I am already telling my students about them !)  Could it be because Fisher and Pearson's main focus was not on Industrial Manufacturing and Business ?   Nevertheless, many of the statistics used today in Six Sigma tools and techniques ( Correlation, Regresssion, DOE , Capability Analysis etc ) are based on the work of either Ronald Fisher or Karl Pearson.  If Walter Shewhart is the Father of Statistical Process Control, then surely Fisher and Pearson are the Grandfathers !