6 )

The difference between the earliest possible starting time and latest permissible starting time for each activity is called the slack for the activity. Slack refers to the amount of delay that an activity could have, relative to its earliest possible starting time, without causing the last activity to be late. Activities that have zero slack are said to be critical. Critical activities cannot be delayed without causing the overall project to be late. The critical activities form a sequence that is called the project's critical path. The critical path for the example in Figures 3.3c and 3.4 is shown in Figure 3.6. Figure 3.7 is a time-scaled version of this critical path.