In general, the PERT longest stretch and or ideal shortest stretch of dependent events should not contain k>=3 stacking risks <=0.50. For example, one path wit

In general, the PERT longest stretch and or ideal shortest stretch of dependent events should not contain k>=3 stacking risks <=0.50. For example, one path with best probable outcomes: [S]->[a]->[b]->[c]->[d]->[E] a=0.73 b=0.49 c=0.33 d=0.50 By taking the 3 lowest/riskiest key deliverables in the best case outcome: 0.49x0.33x0.50 = ~0.08 likelihood of project success This means one should restructure the project, redefine the goal scope, or shelve the project. People that practice this approach say "no" a lot, but the firm does survive. Best of luck, =)