A project is represented by the activity durations (estimated at 90% likelihood of completion)and precedence requirements shown in the table.What is the length of the feeder buffer if this project is managed using critical chain methodology? $$\begin{array} { | l | l | l | l | l | l | }
\hline \text { Activity } & \text { Predecessor } & \text { Length } & \text { Activity } & \text { Predecessor } & \text { Length } \
\hline \mathrm { A } & - & 20 & \mathrm { D } & \mathrm { B } & 16 \
\hline \mathrm { B } & \text { A } & 20 & \mathrm { E } & \mathrm { C } & 8 \
\hline \mathrm { C } & \text { A } & 10 & \mathrm {~F} & \mathrm { D } , \mathrm { E } & 8\
\hline
\end{array}$$
A)9.0
B)7.5
C)4.5
D)6.0

Question

A project is represented by the activity durations (estimated at 90% likelihood of completion)and precedence requirements shown in the table.What is the length of the feeder buffer if this project is managed using critical chain methodology? $$\begin{array} { | l | l | l | l | l | l | } 
\hline \text { Activity } & \text { Predecessor } & \text { Length } & \text { Activity } & \text { Predecessor } & \text { Length } \
\hline \mathrm {  A } & - & 20 & \mathrm { D } & \mathrm { B } & 16 \
\hline \mathrm { B } & \text { A } & 20 & \mathrm { E } & \mathrm { C } & 8  \
\hline \mathrm { C } & \text { A } & 10 & \mathrm {~F} & \mathrm { D } , \mathrm { E } & 8\
\hline
\end{array}$$
A)9.0
B)7.5
C)4.5
D)6.0

Quizplus · Accepted Answer

The critical chain is the longest path considering both task durations and resource dependencies. Here, the critical path is A-B-D-F with a total length of 20+20+16+8=64 days. The feeder buffer is added to protect the critical chain from delays in non-critical paths merging into it. The non-critical path is A-C-E, with a total length of 20+10+8=38 days. The difference between the end of the non-critical path and its merge point into the critical chain (before F) is 64-38=26 days. Since F is the merge point and its duration is 8 days, the feeder buffer is calculated as the difference between the critical path duration up to the merge point (A-B-D = 20+20+16 = 56 days) and the non-critical path duration (38 days), which is 56-38=18 days. However, since the question does not specify how to calculate the feeder buffer directly from the given information and my initial calculation seems to have misinterpreted the standard approach to calculating feeder buffers in the critical chain methodology, let's correct the approach:The correct approach to finding the feeder buffer size involves comparing the lengths of the critical path and the sub-critical path up to the point they converge and then applying a buffer calculation. However, the feeder buffer directly protects the critical chain from delays in feeding paths, not the difference in path lengths. Given the information and typical critical chain methodology principles, without specific buffer calculation formulas provided in the question, the direct calculation of the feeder buffer size from the given data is not straightforward. Critical chain methodology often involves calculating buffers based on the variability and risk associated with task durations, not directly from the path length differences. Therefore, without explicit formulas or risk estimates for each task, determining the exact feeder buffer size from the provided information requires assumptions not given in the question. Revisiting the calculation with the correct understanding that the feeder buffer is designed to protect the critical chain from delays in the paths merging into it and acknowledging a mistake in the initial explanation, the correct answer should be based on the methodology's principles rather than a direct calculation error. Given this, my explanation mistakenly attempted to calculate the feeder buffer in a manner not aligned with the critical chain methodology's standard approach, which does not directly derive feeder buffer sizes from the path length differences as described.

A Project Is Represented by the Activity Durations (Estimated at 90