Project Management Context
Professor C. Lennon
Project managers carefully manage slack on sensitive resource-limited projects (Larson and Gray, p.295). If possible, they will add slack at the end of the project by committing to a completion date that goes beyond the scheduled date. Eliyahu Goldratt (1997) advocates an alternative approach to managing slack. He championed the “theory of constraints” and has coined the term “critical-chain” recognizing that the project network may be constrained by both resource and technical dependencies (Larson and Gray, p.295).
Projects often can exceed their planned schedule by a certain percentage, sometimes even 50 to 100 percent. Often this is attributed to uncertainty or the unforeseen. Managers and project personnel have learned to compensate to this dilemma by adding additional time to their schedule estimates (Larson and Gray, p.302). Yet even when they do, projects still overrun their schedules. Goldratt (1997) argues that there is a natural tendency for people to add safety time, just in case, to their estimations. One of the key problems identified in this case was the project time estimate. Even when management added 10 percent time to all activities or added 10 percent project estimates to ensure project durations would be met, the issues still remained (Larson and Gray, p.302). Then, Pinyarat explained that the activity durations had gotten squeezed down to less than the 50 percent guideline and that the estimates were impossible. Pinyarat also mentioned that she was allowed to put in a big enough project buffer and other members of the firm had no idea why management would use CCPM scheduling in these projects (Larson and Gray, p.303). It is believed that project managers who estimate activity times provide an estimate that has about an 80 to 90 percent chance of being completed on or before the estimated time (Larson and Gray, p.295). Using the Critical...
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