Schedule Risk: 1,000 Project Runs
About this app
Monte Carlo simulation of a network diagram: each run lands as a particle on its end date. Histogram, S-curve, P50/P85, merge gate and criticality index show how safe the trade-fair date is.
With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.
Schedule risk analysis with Monte Carlo
A three-point estimate gives each activity an optimistic, a most likely and a pessimistic duration. Monte Carlo simulation draws many durations from these, computes the network for each draw and collects the project ends. The result is a distribution instead of a single number. P50 is the date met by half of the runs, P85 the date met by 85 percent. Because activities can take much longer but hardly shorter than expected, the mean lies above the most likely value.
What the app shows
Each of the 1,000 runs of the case project Lumen (fictional) falls as a particle onto its end date. This builds a histogram and an S-curve with P50 and P85, plus lines for the plan in week 28 and the trade fair in week 30. A merge gate before activity G shows why a surcharge arises: the maximum of the predecessors counts. The criticality index states how often each activity lay on the longest path. Distribution (PERT beta or triangular), uncertainty and pessimism can be set.
Things to try
Send a single run slowly through the network and watch the merge points. Compare the calculation along the critical path only with that of the whole network: the whole network ends later. Raise uncertainty or pessimism and watch P85 move. Move the start forward to build buffer before the fair. Switch on the sample risk register and the firmware measure that lowers the likelihood of the risk on activity D from 30 to 10 percent.
Frequently asked questions
- What do P50 and P85 mean for schedules?
- P50 is the project end met in half of the simulated runs, P85 the end met in 85 percent of them. P85 is often used for a commitment or to size a reserve, because it deliberately sits on the safe side.
- Why does the simulated project end come later than the plan?
- The plan uses the most likely durations. Three-point estimates are skewed to the right, and at merge points the maximum of the predecessors decides. So even activities with float can delay the end. Together this shifts the distribution of project ends to the right.
- What is the criticality index?
- The criticality index is the share of runs in which an activity lay on the longest path. It shows which activities carry the schedule risk, even if they have float in the deterministic plan.
- Which model does the app use?
- The app uses a Latin hypercube sample with a fixed seed, so every visit shows the same picture. Durations follow a PERT beta distribution with weight 4 or a triangular distribution. Case project and risk register are invented.
Subject: Projektmanagement
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