In addition to using task relationships to define your project schedule, you can modify when a relationship goes into effect using Lag and Lead options. As you create relationships, you will see the Lag box in both the Task Dependency dialog box and the Task Information dialog box. Lag and lead time are both entered in the Lag box.
Lag time is any amount of time you need to account for between the completion of the predecessor task and the start of the successor task or the start of one task and the start of another. This always depends upon the type of assigned task dependency. However, in every case lag time inserts a delay between two tasks and is always entered as a positive number.In the above figure, notice the three-day buffer between the completion of Task 11 and the beginning of Task 12. This is lag time. You will see lag time denoted on both the Gantt Chart and in the Predecessors column in the Entry table. In the above figure you can see that the lag time has been entered as a duration based on days. You can use any duration time to define your lag time. Additionally, you can use a percentage to designate that a successor wait a length of time equal to the percent entered based on the predecessor task duration. For example, if the predecessor task is two days and a lag time of 50 percent is entered, the total time between tasks is equal to one day (typically eight hours). To enter lag time, follow these steps:
- Create a relationship between two tasks.
- Open the Task Information dialog box for the successor task.
- View the Predecessors tab.
- Enter a positive number or a positive percentage in the Lag column next to the task's predecessor.
- Click OK.
If you decide later that the lag time is too long, perhaps that only two days are needed for the boss to approve the procurement template instead of three, you can change the lag time in a number of ways.
You can open the Task Information dialog box again and use the Predecessors tab, or you can edit the lag time in the Task Dependency dialog box or in the Entry table.
To change the lag time using the Task Dependency dialog box, double-click the link in the Gantt chart between the tasks to open this dialog box and change the lag time as appropriate. To change the lag time in the Entry table, select the Predecessors column for the task and change the number after the + sign to the number you want the lag time to be.
With permission from Microsoft Press, this article content was excerpted from the book, Managing Projects with Microsoft Office Project 2007 (Self-Paced Training Kit for Exam 70-632).