It’s a good idea to save your project file just before calculating PERT.When you click the Calculate PERT button, you’re prompted to confirm the calculation.
When you click OK to confirm the deletion, only tasks with PERT estimates are calculated. Figure 13.5 shows the Develop Proposal task, before and after PERT Calculation.
Using the PERT Views
After you enter PERT duration, you can switch between expected, pessimistic, and optimistic views of the project’s Gantt Chart, whether or not you calculate duration using PERT.Figures 13.6 and 13.7 contrast the Pessimistic and Optimistic Gantt Charts for a portion of the XYZ BOT project. To display the Pessimistic Gantt Chart, make sure that the PERT Analysis Toolbar is displayed (View> Toolbar > PERT Analysis), and click the Pessimistic Gantt button.
To display the Optimistic Gantt Chart, click the Optimistic Gantt button on the PERT Analysis toolbar. In Figure 13.7, the optimistic finish date is eight days before the pessimistic finish date .
To display the expected project schedule, click the Expected Gantt button on the PERT Analysis toolbar.
The Mathematics of PERT
Imagine twenty projects that include the same task: Task A In each project, Task A was completed in an actual number of hours. A review of the actual hours for this task in each of the 20 projects looks like this.
Actual hours range from a low of 16 to a high once average is 23~55 hours. Was created a column chart to show the frequency of each of the actual hours values. the mart is dose to the be U curve normal d!distributional result ‘of plotting frequency of random variable.
PER Trellises on a normal distribution to describe the variability in duration. If we added data from .100 projects that induced Task A. we would expect that the wipe would become even more normal, mustered around the average time of 23.55 hours, and that it would be four times more likely that the dual hours would be between 23 and 24 than 16 or 32 hours. PERT analysis assumes that-every project task, if repeated enough times, would yield a normal distribution such as the distribution shown previously. The optimistic and pessimistic PERT estimates provide the range’ of the distribution used to adjust the expected value to determine PERT duration. If you believe that the normal distribution doesn’t accurately describe the potential variation in a task’s duration, you can change the weights that Project 2000 uses to calculate the PERT duration.
Changing the PERT Weights
The PERT weights assume the normal distribution that’s observed with a random variable (see “The Mathematics of PERT”in the previous sidebar), If there is evidence that the distribution of duration for an entire project will not be normal, you can change the weights given to each of the three duration when PERT calculates duration to better reflect the skew in the distribution. The default values are 1 for optimistic, 4 for expected, and 1 for pessimistic. When you change these values, the total must still equal 6. To change the weights, click the Set PERT Weights button to open the Set PERT Weights dialog box:
Viewing the Critical Path
Critical Path method and PER Tare closely related, and have become intertwined during nearly four decades of use in project management. Originally designed for deterministic projects, the CP1 is used to highlight high-risk tasks in a project.
It doesn’t matter that the duration for the critical tasks were developed with PERT methods.
CPM is a method used to analyze the relationships between activities in a project. The critical path is the series of interrelated tasks that takes the longest time, so it therefore affects the projected finish date. To see the paths in a project file, display a network diagram by choosing View> Network Diagram from the menu. The network diagram is a flowchart of the project activities the network diagram for the XYZ BOT project.
Each task that appears is in an individual box. Summary tasks are parallelograms, whereas tasks are displayed in rectangular boxes. Click the expand or collapse buttons above summary tasks to show ride summary task’s sub tasks, Double-click a task box to open the Task Information Form for the task. If you prefer the network Diagram to the Gantt Chart view, you can create or remove task dependencies and assign resources in this view.
The lines between tasks are the dependencies created by using tpe Link Tasks button. To display more of the project, choose View> Zoom from the menu to open the Zoom dialog box, shown next.
The smallest zoom is 25%. If you choose Entire Project and your project can’t be displayed in its entirety. at 25%, you’ll be prompted to accept the 25% setting:The critical path for our project starts in the upper-left. corner and continues across the bottom of the application window,The Network Diagram increases in utility as the project progresses. You can use filters in the Network Diagram as you would in the Gantt Chart view, so you can, for example, display only critical tasks, tasks that are over budget, or slipping tasks. Figure 13.10 shows the XYZ-BOT project’s slipping tasks.With this filter, you can tell which slipping tasks require your attention-the tasks on the screen that are red and bold because they lie in the critical path.
No matter how closely you manage risk in your projects. success cannot be achieved without effective communication with and management of the various projects.
In “Sharing Resources and Tasks among Various Projects,” we’ll explore how to share resources and tasks across multiple projects, In IS, “Communicating Project Information” and , “Team Project Management with Project Central 2000 we’ll show you how to use Project to effectively communicate with your project team.