Neal Whitten's No-Nonsense Advice for Successful Projects

CHAPTER 34

The S-Shape Curve 50/70 Rule

Various models are used to predict an activity’s percent complete based upon time expended. Two common, but typically ineffective, models are the linear 50/50 rule and the S-shape curve 50/50 rule (depicted in Figure 34-1), both used for equivalently weighted tasks (i.e., tasks of approximately the same level of effort). Have you ever noticed that both the linear and S-shape curve 50/50 rules do not seem to work well on your projects?

The 50/50 rule states that an activity should be 50 percent completed when half the allotted time has elapsed and should be 100 percent completed when the other half of the allotted time has expired. The linear 50/50 rule is an instance of the 50/50 rule depicted as a straight ...