Projects Frequently Overrun Schedule

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When asked why projects overrun schedule, people usually say the projects start out fine, but somewhere along the way, a snag develops that begins to push one or more deliverables farther and farther behind. Everyone knows that it only takes one late

Figure 3.7 Task time conflict.

task on the critical path to make the whole project late. As this shift begins to hit the plan, management tries to solve the problem causing the shift, usually by diverting resources and making changes in the project plan, placing more and more emphasis on the part of the plan that is slipping. The people working on the snag usually feel a lot of pressure to get their part of the project solved and, therefore, put in a lot of extra time and feel considerable stress. These are often the resources in most demand in the company, so putting more time on the project in trouble leads them to neglect the other projects they are supposed to be working on, causing other projects to slip as well.

When asked why this happens, people respond with two general types of answers. One type of answer focuses on the specific problem with the specific project that is most recent in memory (often still in trouble). They usually blame the slippage on poor performance by the group responsible for that part of the project. The second type of response is more general, blaming the slippage on the tendency of stereotypical task performers to underestimate or on management's setting arbitrary completion dates.

How often do people complete activities and pass their work on early? How often do they complete activities for less than the budgeted activity cost? You might find this occurs less frequently than you expect, if the estimates are truly 90% probable estimates. Even with skewed distributions, tasks should complete early a substantial percentage of the time. Figure 3.8 illustrates typical results for the actual times that project tasks take as compared to their planned duration. Most tasks complete exactly on the due date; often as many as 80% complete on the due date. This is not consistent with the task-completion-time estimate presented earlier.

Potential causes for little positive variation in activity duration or cost include the following:

1. People work diligently to milestone dates and do not understand a desire to have the work completed early.

2. Estimates are much less probable than we believed, leaving little potential for positive variations.

3. The work expands to fill all available time and budget.

4. There is a belief that the next activity will not be ready to use the work anyway.

5. In most organizations, there are significant penalties (threatened or real) for completing activities late. What are the rewards for completing activities early?

6. Reduced budget for the performing organization leads to higher overhead rates and, in extreme cases, downsizing.

7. Reduced credibility of performer's activity duration and cost estimates leads to increased pressure to reduce the estimates.

These factors add to the psychological reasons that cause projects to lose much potential positive variance. Project managers assign tasks and train people to respond to specific milestone dates. Thus, even if they are done early, they might hold on to the product until the due date. Why not? Management usually does not take advantage of early completion or reward the task performers if they do deliver

Figure 3.8 The distribution of actual task completion time differs from the estimate distribution. It shows a remarkable percentage of completions right on the due date.

early. Paying the resource performing the work in accordance with the time they spend on the task motivates him or her to use all of the resource authorized. Using a "cost-reimbursement" contract with the resource (the usual practice for resources in the company and for certain types of external resources) may provide him or her incentive to slow down the work to get overtime pay or more total revenue from the project.

If one resource gets an activity done early, what is the chance that the next critical resource down the line is ready to hop to and start working on his or her activity? If it is a critical resource, it is in demand and has limited availability. It does not seem likely that resources will be able to work on activities until the scheduled dates. Therefore, we lose the positive variance and introduce wait time. This means that the actual schedule time grows due to activity dependence.

All of this leads to the second conflict illustrated by Figure 3.9. The upper path refers to the performing resource. In order to be a successful team member, I must

Figure 3.9 The conflict underlying project schedule overruns.

contribute to early completion of the project. In order to contribute to early completion of the project, I must turn work in early. On the lower branch, in order to be a successful team member, I must have sufficient time in my task estimates to complete my commitments. In order to have sufficient time to complete my commitments, I must not turn tasks in early. The obvious answer to this is that I can always do extra checks and improve the quality of my project-task result when it looks like I might finish early. Even if I do finish early and turn the work in to my manager to be checked prior to submitting it to the project, she will not likely look at it until it is due anyway as she is a very busy person.

Student Syndrome Did you always study for your exams weeks ahead so that you could go to bed early the night before? Did you always write your papers to get them done at least a week before the deadline to avoid the gap in the library where all the books on the topic used to be and to get to the college computers before everyone else was on them all night? (They did not have computers when I was in college, so this was not a problem for me.) Are you normal?

Well, it is probably not news to you that you are normal and that most people have a tendency to wait until tasks get really urgent before they work on them. This is especially true for busy people in high demand, that is, all of the most important people that the project manager is counting on to get the critical-path work done on time.

Figure 3.10 shows the typical work pattern of many people. They do less than a third of the work on an activity during the first two thirds of the activity duration. They do two thirds of the work during the last third of the activity duration. Where are they more likely to find they will have a problem completing the activity in the remaining time: during the first third of the effort or during the last third? If they are working above 100% capacity already to complete two thirds of the work in one third of the time, there is no chance of keeping to the activity duration by putting in a little extra effort. What is the chance they can recover from an unanticipated problem, like a computer crash?

Figure 3.10 People perform most activities, and most people follow the student-syndrome performance curve.

Milestone date

Effort

Milestone date

Effort

Figure 3.10 People perform most activities, and most people follow the student-syndrome performance curve.

Activity time

Activity time

Student-syndrome behavior results in there being little chance of seeing the positive side of activity duration variation. The effects described above make it unlikely that we could take advantage of positive variation, even if we did see it. No wonder projects rarely complete early! The reality is that relative activity duration normally shows a very skewed distribution, with a mean well above the average activity time. This is one reason why we often see overruns on activity time, but rarely see underruns.

Most project-management guidance recommends that project managers use an early-start schedule. This means they start all of the non-critical-path activities earlier than is necessary to meet the schedule date. People working on those activities know that there is slack in their activity. How do you think this influences the urgency they feel in working on the activity?

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