Prerequisite College Statistical Math for Six Sigma - Refresher Training, 7 Hours for Six Sigma Green Belt or Yellow Belt. You need to complete this class before taking SSGB or SSYB training if this math area is weak. There's a lot of math in the Six Sigma Classes, more in the Green Belt class. Training must have taken college algebra. This class prepares the trainee for a Six Sigma Green Belt or Six Sigma Yellow Certification Training who require a math refresher.