The Critical Chain Scatter Plot Movies

The key performance indicator in a project organization managed according to Critical Chain is the portfolio overview provided by a scatter plot. In a scatter plot diagram you have a complete overview of all projects and how they are progressing.

There are typical patterns to how these scatter plots change. It’s important to understand what causes these patterns in order to react quickly and precisely and to secure the positive effects of Critical Chain.

The “Scatter Plot Movie Maker” was designed to better understand the cause-and-effect chains. It is a small multi-project simulation that enables us to experiment without having a real operational impact.

On this webpage you’ll find five scenarios. The first two are tutorials about how to use the “Scatter Plot Movie Maker” and to verify whether it is correctly implemented. If you are interested in the results and familiar with CCPM then you can go directly to parts III to V.

  • Part I "One Single Project" shows how a project is defined in the Scatter Plot Movie Maker and what a typical fever curve looks like.
  • Part II "Three Projects Fighting for Resources" shows three projects competing for one resource. You can already see how the operational CCPM priorities work.

The scenarios 3 to 5 contain answers to dedicated questions:

  • Part III "One Big Elephant" shows what happens if, in a well-staggered portfolio, an additional project is introduced – and, in this example, it is not even a big elephant.
  • Part IV "How to Repair a Broken Project Portfolio" shows how CCPM works to fix a broken portfolio. It is very interesting to note that you need fewer resources compared to traditional approaches.
  • Part V "How to Destabilize a Project Portfolio" is a short example, showing how you can easily destabilize a perfect project portfolio.

If you want to try it yourself you can request the "Scatter Plot Movie Maker" here ...

And now to the content and learning:

Part I - One single Project (Video):

  • How to use the “CCPM Scatter Plot Movie Maker” and define projects.
  • The fever curve is even in a perfect world, with no disruptions and no estimation errors, a small curve. This is simply caused by the progress on the Critical Chain is calculated and has no negative influence in practice.

Part II Three Projects Fighting for Resources (Video):

  • How to set up a portfolio of projects and define the simulation parameters.
  • The influence of a constraint is much greater than first thought. Even if you do not subordinate willingly the constraint works like a valve – and in all process steps downstream from the constraint it will look like the projects are perfectly prioritized.
  • If the constrained resource is located near the beginning of a project, by forced staggering the projects we can see that downstream the priorities don’t change any more – even if a near constraint follows.
  • After a “physical” (forced) staggering, it can happen that one project is delayed more than others. You need to use CCPM operational priority for this effect to be reduced. The downstream stages simply prioritise the project with the worst progress and the highest buffer consumption.

Part III One Big Elephant

Learnings (Video):

  • In a CCPM-managed portfolio there are two states: WIP under control and WIP not under control.
  • In the case where the WIP is under control, the projects move upwards on the 45° diagonal. Even if there is a lot of protective capacity, the projects follow the 45° diagonal – there is no “green shift”.
  • In the case where the WIP is not under control, the projects don’t follow the red-yellow line as expected. This is simply because the operational priority is calculated by the quotient of progress on the Critical Chain and by buffer consumption and has no connection to the red-yellow line definition.
  • When a temporary overload is induced (e.g. by an additional unplanned/unstaggered project or “elephant”) all active projects shift to red. They suffer equally for as long as the additional project is active. When the additional project is completed, everything goes back to normal.
  • Even one additional project has a huge influence on the due-date reliability of all currently active projects. The effect is much bigger than expected.
  • The effect on the lead time is immense. The elephant in this example with something around 20% additional demand in capacity caused an increase in lead time of about 32%. This can easily explained by Little’s Law and increasing desynchronization.
  • CCPM helps to stabilize the situation and avoids wide deviations in buffer consumption and unfairness between the projects.
  • Using CCPM, portfolio management is stable even under such circumstances and heals itself.

Part IV: How to Stabilize a Project Portfolio (Video):

  • If you apply CCPM operational priorities to a broken portfolio, it stabilizes within a short timeframe and balances out the due-date deviations – but it cannot avoid a delay to all projects.
  • If you want to avoid the delay by setting up project budgets/teams so each project/team has its own resources, it will stabilize the situation. But there is no improvement beyond the situation not getting worse. Projects with high buffer consumption keep their critical status. To get the “black” projects back to red (on track for meeting their due-dates) even more resources are needed.
  • Using the Critical Chain operational priority in combination with a few additional flexible resources will very quickly bring even the worst projects back in line without hurting the good one very much. To recover the projects and keep the promised due dates you need significantly less resources, compared to the traditional approach.

Part V: How to Destabilize a Project Portfolio (Video):

  • This example shows what happens when you don’t follow the CCPM rules and install project budgets. It shows how easily you can destabilize a whole project portfolio.