Six Sigma processes

are based on three principles: $(1)$ all work is a statistically controllable process; $(2)$ no well$-$controlled process allows variability; and $(3)$ defect$-$free work requires tight statistical controls.

can be used for both improving existing business processes and for developing new processes or products.

can be used for improving products or business processes but not for developing new products or new processes.

consists of a disciplined, statistics$-$based system aimed at producing not more than $10$ defects per million iterations for a manufacturing or assembly process.

can be used for developing new products or new business processes but not for improving existing products or business processes.