Project Management PHẦN 5 docx

Figure 5-4. Task list with dependencies.

Next, validate the dependency analysis worksheet. All task identifiers must appear in the Immediate

Predecessor column unless the task is one of the last in the project. Look down the Immediate Predecessor

column and determine if every work task identifier (in your WBS) appears. If it does not, ask, “Is this one of

the final tasks of the project?” If the answer is yes, the WBS is validated. If the answer is no—that is, it isn’t

the last or one of the final tasks in the project—you have forgotten to make it a predecessor to something.

Check your logic.

Now plot the work tasks onto the network. Draw a Start box on a blank sheet of paper in the vertical center

toward the far left of the paper (the planning chart will branch to the right, top and bottom). At the Start box,

burst all of the starting work tasks. In our example, we have only one starting task, Task A. Draw a

dependency arrow from the Start box to each of the starting tasks (again, work tasks with no predecessor).

Build the chain by taking any task (or combination of tasks) now diagrammed on the network and searching

for them in the immediate predecessor column. When you find them, expand the network accordingly. Let the

immediate predecessor column drive the interpretation onto the network. You are developing a series of

chains; each activity that appears on the network is merely a link in that chain. Once the link is attached to the

chain, the Immediate Predecessor column tells which link or links must be attached next. Figure 5-3 shows

how to use multiple dependency arrows when two or more activities burst out or converge; Tasks C, D, and E

all share the same predecessor, Task B. Use the following guidelines when developing the network chart:

Guidelines for Developing a Network Chart

• Don’t worry about time estimates or drawing the network chart to scale. Concentrate on the

relationships. The chart aesthetics can be improved later.

• Make sure there is only one Start box and one End box.

• Do not allow any task to dangle. Every task must connect to another task or to the start or end of the

project. In other words, every task must be integrated into the framework of the network chart. If

several tasks are all ending tasks, tie them together to one End box.

• Indicate key go/no-go points in this network chart.

• Remember that this is a communication tool; it must be clear to all who use it.

Estimating Techniques

Estimating is not your best guess. It is not trying to reach a challenge. It is not succumbing to somebody else’s

demands. Here are a few more examples of what estimating is not: an estimate is not what we estimated the

last time; not what we estimated the last time plus how much we slipped; not a conservative number with lots

of padding; not taking someone else’s estimate and then doubling it, and then increasing the units of time by

one; not providing the expected or “right” answer.

Remember, the word estimate is defined in Webster’s Tenth New Collegiate Dictionary as “an opinion or

judgment of the nature, character, or quality of a . . . thing” or “a rough or approximate calculation.” Many of

us think of an estimate in these terms. However, the dictionary also defines an estimate as “a numerical value

obtained from a statistical sample and assigned to a population parameter.” That means that an estimate can

and should be more than a guess, educated or otherwise. We will look at a technique that can make your

estimates more credible (with exertion and effort, though).

Estimating in project management is a forecasting technique for determining the amount of effort time and

elapsed time required to complete the work tasks of a project. We are attempting to forecast or predict how

long the actual effort or work will take, how many human resources will be required, and the elapsed time or

duration for completing the tasks.

Figure 5-5 shows a framework for developing a forecasting model. In order to determine the effort time and

elapsed time required to complete a project task, we need to consider the key variables that affect it. (Effort

time is defined as the amount of a person’s actual effort given to the task. Elapsed time is the duration

between when the task begins and ends.) For example, in the blank circles marked with directed forward

effort, we could write the key variables that affect our estimates of the time to complete some of the work