1. Introduction
A project is a temporary endeavor with a defined beginning and end, undertaken to meet unique
goals and objectives and to create beneficial or added value. The classic project triangle shows
the trade-off between cost, time and specifications, where improving one dimension typically
affects the others
Scheduling covers all static planning work done before project execution, whereas control
refers to dynamic activities during project progress.
Risk analysis forms a feedback loop between scheduling and control: risk is analyzed in advance
in a static way, while actual risk happens during the dynamic execution phase.
Project mapping positions projects along two axes: complexity (resources) and uncertainty
(risk).
• Low uncertainty and low complexity lead to baseline scheduling with
PERT/CPM. Example: Fabricom: luggage systems, 5-6 people, no huge risk.
• High risk and low complexity lead to Scheduling Risk Analysis (SRA). Example:
Brabantia, 3-4 people, marketing success defined at the end = risk.
• High complexity and low risk point to Critical Chain scheduling (CC). Example: Water
infrastructure.
• High complexity and high risk lead to Critical Chain/Buffer Management (CC/BM),
where buffers are added to protect against risk. Example: NPD, development iPhone: no
idea what to expect at the end of the project.
2. Baseline Scheduling
2.1. PERT basics
PERT (Program Evaluation and Review Technique) uses three time estimates for each activity: a
(best), m (realistic), and b (worst). Activity durations are assumed to follow a right-skewed beta
distribution, closer to the worst case than to the best case.
Formulas:
• Expected duration: (𝑎 + 4𝑚 + 𝑏)/6
• Standard deviation: (𝑏 − 𝑎)/6
The procedure is:
1. Define three time estimates per activity.
2. Compute average and standard deviation per activity.
3. Determine the average critical path duration.
4. Apply the Central Limit Theorem to approximate total project duration.
5. Use statistical insight to support decisions.
, 2.1.1. Strengths & Weaknesses
Average of CPM close to 50/50, but actual 44/56 (error is low)
• Estimates are human input (3 estimates better than 1, “garbage in, garbage out”)
• Simplifications of statistics (assumption no correlation: standard deviation)
• PERT ignores non-critical activities (can become critical -> stdev & CLT not correct)
2.2. CPM and the project phases
CPM (Critical Path Method) focuses on deterministic durations and is especially suited to low
complexity, low risk projects. Capacity increase (new water towers, pipeline, machines,
buildings): not easy but not extremely complex.
The logic of phases:
• Concept →
• Definition (what?), static →
• Scheduling (when?), static →
• Execution, dynamic (Mister Murphy) →
• Control →
• Termination.
In the definition phase, a global plan is prepared, including:
• A(1): determination of activities via a Work Breakdown Structure (WBS)
• P(2): responsibility assignment (possibly external experts)
• L(3): sequencing and linking of activities
• N(4): network analysis providing input for scheduling tools (output of definition phase)
The WBS breaks down the project objective into
• Root node
• Work items (building machines, define work items -> expertise) (not only 1/WI)
• Work packages
• Activities
Where the lowest level corresponds to the highest level of detail; each level has a specific
functionality.
This is related to the Organization Breakdown Structure (OBS): project objective → work items
→ work packages → activities.
VMW definition phase with two parts (reservoir and new machines) due to different objectives
(time vs cost).
Part1: increase reservoir: very urgent, more water during peak needed now!!: obj = time
Part2: new machines for bigger capacity not so urgent (more demand only in 6-7 years) obj: cost
A project is a temporary endeavor with a defined beginning and end, undertaken to meet unique
goals and objectives and to create beneficial or added value. The classic project triangle shows
the trade-off between cost, time and specifications, where improving one dimension typically
affects the others
Scheduling covers all static planning work done before project execution, whereas control
refers to dynamic activities during project progress.
Risk analysis forms a feedback loop between scheduling and control: risk is analyzed in advance
in a static way, while actual risk happens during the dynamic execution phase.
Project mapping positions projects along two axes: complexity (resources) and uncertainty
(risk).
• Low uncertainty and low complexity lead to baseline scheduling with
PERT/CPM. Example: Fabricom: luggage systems, 5-6 people, no huge risk.
• High risk and low complexity lead to Scheduling Risk Analysis (SRA). Example:
Brabantia, 3-4 people, marketing success defined at the end = risk.
• High complexity and low risk point to Critical Chain scheduling (CC). Example: Water
infrastructure.
• High complexity and high risk lead to Critical Chain/Buffer Management (CC/BM),
where buffers are added to protect against risk. Example: NPD, development iPhone: no
idea what to expect at the end of the project.
2. Baseline Scheduling
2.1. PERT basics
PERT (Program Evaluation and Review Technique) uses three time estimates for each activity: a
(best), m (realistic), and b (worst). Activity durations are assumed to follow a right-skewed beta
distribution, closer to the worst case than to the best case.
Formulas:
• Expected duration: (𝑎 + 4𝑚 + 𝑏)/6
• Standard deviation: (𝑏 − 𝑎)/6
The procedure is:
1. Define three time estimates per activity.
2. Compute average and standard deviation per activity.
3. Determine the average critical path duration.
4. Apply the Central Limit Theorem to approximate total project duration.
5. Use statistical insight to support decisions.
, 2.1.1. Strengths & Weaknesses
Average of CPM close to 50/50, but actual 44/56 (error is low)
• Estimates are human input (3 estimates better than 1, “garbage in, garbage out”)
• Simplifications of statistics (assumption no correlation: standard deviation)
• PERT ignores non-critical activities (can become critical -> stdev & CLT not correct)
2.2. CPM and the project phases
CPM (Critical Path Method) focuses on deterministic durations and is especially suited to low
complexity, low risk projects. Capacity increase (new water towers, pipeline, machines,
buildings): not easy but not extremely complex.
The logic of phases:
• Concept →
• Definition (what?), static →
• Scheduling (when?), static →
• Execution, dynamic (Mister Murphy) →
• Control →
• Termination.
In the definition phase, a global plan is prepared, including:
• A(1): determination of activities via a Work Breakdown Structure (WBS)
• P(2): responsibility assignment (possibly external experts)
• L(3): sequencing and linking of activities
• N(4): network analysis providing input for scheduling tools (output of definition phase)
The WBS breaks down the project objective into
• Root node
• Work items (building machines, define work items -> expertise) (not only 1/WI)
• Work packages
• Activities
Where the lowest level corresponds to the highest level of detail; each level has a specific
functionality.
This is related to the Organization Breakdown Structure (OBS): project objective → work items
→ work packages → activities.
VMW definition phase with two parts (reservoir and new machines) due to different objectives
(time vs cost).
Part1: increase reservoir: very urgent, more water during peak needed now!!: obj = time
Part2: new machines for bigger capacity not so urgent (more demand only in 6-7 years) obj: cost
