Friday, December 28, 2012

The Schedule – Risk Buffers

“The first step in the risk management process is to acknowledge the reality of risk.  Denial is a common tactic that substitutes deliberate ignorance for thoughtful planning.”
                                                                                                                - Charles Tremper

With this post, we conclude the series on developing the well-formed schedule.  We have taken the WBS, which defines the project scope, added the task dependencies, estimated the effort for each task, assigned resources to each task, and resource-leveled the task assignments.  The final step to complete the well-formed schedule is to add risk buffers so that the schedule has the intended probability of success.
A schedule without risk buffers has virtually no probability of success.  Since you probably want to present a schedule with some probability of success, it obviously follows that you must add some risk buffers.  So now you probably want me to tell you how many and where.

I’ll briefly identify two common practices for identifying risk buffers.  The first is built from the standard risk management process.  The PMI PMBoK risk management process includes the step “Quantify risks.”  You’ve probably wondered what this means.  For risks that should be mitigated, determine the probability of occurrence (a percentage) and the time and cost that must be added to the project if the risk event occurs.  Let’s say for a specific risk you determine there’s a 25% probability that it will occur and that if it occurs it will add 12 weeks (I’m just going to deal with time in this example, but you can extrapolate for costs) to the schedule.  The 25% probability times the 12 weeks is 3 weeks, meaning that you should add a risk buffer of three weeks to your schedule.
Depending on a variety of factors, you can either add all three weeks to the end of the schedule or spread it in appropriate points over the life of the project.

You repeat this for all significant project risks.
A very common alternative to this approach is to use the Critical Chain approach developed and promoted by Elihayu M. Goldratt.  It uses a formulaic approach to determine the appropriate amount and placement of the risk buffers.

This overview is obviously too high a level for practical application.  But with this post I’ve finally presented enough of the PM foundation so that I can introduce some of the more interesting and complex concepts.  I’ll do this starting with a couple of posts on advanced quantification of the schedules, then maybe transition to more fully explaining the development of risk buffers.
It’s taken me two years of posts to get to “the fun stuff.”  What area of project management best practice would you like me to tackle?

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