$1.$ Six Sigma processes:

Are based on principles: $(1)$ all work is a statistically process; $(2)$ all processes create data that explain variability

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 $100$ iterations

All of the above

Both $1$ and $2$