In 6 sigma project ,in DMAIC model For define phase how can I define the project due to 4 or 6 or... sigma ?How can I measure and specify the project?In define phase which methods can I used and how an I use?And in measure phase ,is normality import

In 6 sigma project ,in DMAIC model For define phase how can I define the project due to 4 or 6 or... sigma ?How can I measure and specify the project?In define phase which methods can I used and how an I use?And in measure phase ,is normality important for project?If the result cant provide normality what can I do? Thanks...