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l This example illustrates how multitasking can delay task completions. Multitasking also often involves wasted setup time, which increases total duration.
l 2.5 Schedule Development
l Critical chain scheduling assumes that resources do not multitask or at least minimize multitasking.
l Someone should not be assigned to two tasks simultaneously on the same project when critical chain scheduling is in effect.
l An essential concept to improving project finish dates with critical chain scheduling is to change the way people make task estimates.
l Many people add a safety or buffer, which is additional time to complete a task.
2.5 Schedule Development
l Critical chain scheduling removes buffers from individual tasks and instead creates a project buffer.
l In order to ensure that the critical activities are completed on time, buffers are used.
l A buffer is time that is included in the schedule to protect it against unanticipated delays and to allow early starts.
l Critical chain scheduling protects tasks on the critical chain from being delayed by using feeding buffers.
l 2.5 Schedule Development
l Project Buffer is additional time added before the project's due date.
l Feeding buffers are placed at each point where a noncritical activity is related to a critical path activity.
l Feeding buffers protect the critical activities from tasks that precede them and allow for early starts of critical.
l Feeding buffers are additional times added before tasks on the critical chain that are preceded by non-critical-path tasks.
2.5 Schedule Development
Figure provides an example of using critical chain scheduling.
Note that the critical chain accounts for a limited resource
the schedule includes feeding buffers and a project buffer.
The tasks marked with an X are part of the critical chain.
2.5 Schedule Development
Buffers are viewed as different than slack.
l slack is spare time.
l buffers are time blocks that are not expected to be used for work time (the same as slack),
l they are dedicated to cover most likely contingencies,
l if they are not needed, subsequent activities can proceed at the earliest time possible.
l Project buffers are used after the final task of a project to protect project completion time from delays (managing reserve).
3 Cost Planning
3.1 Cost Estimating Techniques
3.2 Cost Budgeting
3.1 Cost Estimating Techniques
Top-Down Estimates
Bottom-Up Estimates
Parametric Modeling
Problems with IT Cost Estimates
Sample Cost Estimate
3.1 Cost Estimating Techniques
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| Pauses or delays between activities are indicated in the network diagram. | | | Top-Down Estimates |