HomeTroubleshooting@RISK with ProjectsError in Outputs with RiskBranch Function (@RISK 4.x)

6.22. Error in Outputs with RiskBranch Function (@RISK 4.x)

Applies to:
@RISK for Project 4.x

Problem:
I looked at the data from my @RISK for Project simulation, which has probabilistic branching. Some of my outputs show "Error" for some iterations instead of giving a data point for that iteration. What is wrong?

Response:
This is an intentional part of the design.

In each iteration, the branching function chooses one of the possible branches. A branch that is not chosen is symbolically removed from the project by "zeroing out" the affected tasks and their descendants. When a task is zeroed out, any outputs related to that task will return "Error" instead of a value. This prevents the values in zeroed-out branches from skewing the summary statistics for that task.

For example, imagine that task A branches with 50% probability to task B1 and 50% probability to B2. If we have outputs on the finish date of B1 and the finish date of B2, and if we run 100 iterations, we would expect the output for B1 to have 50 errors and the output for B2 to have 50 errors. The remaining, non-error samples give us a picture of how the output behaves when the task is included in the project.

last edited: 2012-11-22

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