Waiver Written authorization to use or release a quantity of material, components, or stores already manufactured but not conforming to the specified requirements.
walkthrough. See: code walkthrough.

X & R CHARTS A control chart which is a representation of process capability over time; displays the variability in the process average and range across time.

XmR Charts Control chart which uses a moving range. Typically two but can have a larger range.

ZD Zero Defects

Zero defects Philip Crosby's recommended performance standard that leaves no doubt regarding the goal of total quality. Crosby's theory holds that people can continually move closer to this goal by committing themselves70 to their work and the improvement process.