Dictionary of Lean Six Sigma Tools/Concepts

A statistical control chart that uses a Poisson distribution to measure the proportion of defectives per unit in a sample. It is primarily intended for evaluating discrete (a.k.a. attribute or categorical) values.
Related StatStuff Video: 
   -Section 8-Control Phase, Lesson #7 - Control Charts: U Chart

See Control Chart Control Limits.

A statistical reference for the upper level target of a continuous data point defined by the customer such that anything above it is considered a defect or not meeting the customer's needs (a.k.a. voice of customer or VOC). It essentially represents the maximum measurable point of tolerance for the customer. This is contrasted with the lower specification limit (LSL).
Related StatStuff Video: 
   -Section 5-Measure Phase, Lesson #21 - Defining the VOC and Defects