The statistical thinking underlying Six Sigma is based on the following three principles:

$($i$)$ all work is a sasistically controllable process; $(2)$ no well$-$controlled process allows variability; and $(3)$ defect$-$free work requires tight statistical contersh.

Al work is subject to varying performance outcomes, the amount of walability can be reduced with proper use of statistical methods and controls, and varability declines as tighter and sighter statistical contels are applied.

Al work activites can be done accurably most of the time, empouered employes are necessary for effective control, and Qood statistical deta is an empowered employee's best cortrol thogl.

Ju work is a procesi, al processes have variability, and al processes owate data flat explains variability.