# Re: [Planner Dev] Uncertainty management / MonteCarlo simulation

• From: Santiago Erquicia <serquicia argentina com>
• To: Planner Project Manager - Development List <planner-dev lists imendio com>
• Subject: Re: [Planner Dev] Uncertainty management / MonteCarlo simulation
• Date: Thu, 01 Apr 2004 19:46:16 -0600

```On Thu, 2004-04-01 at 18:03, Mark Durrenberger wrote:
> Comments in Line...
>
> >I think that you can just get the result of the simulation and take the
> >frequency with a given precision.
>
> Not sure what you mean by this.

I'll try to draw it today and send it to the list.

>
> >   In the Gantt view what you are doing
> >actually is scheduling, so you should be able to chose the start and
> >finishing date to a given percentage of the probability to make it.
>
>
> >Of
> >course when the task is always away of the critical path you can choose
> >any number.
> Actually one of the values of Monte Carlo is to see what the "most
> probable" critical path is and for many projects there are multiple
> critical or near critical paths.  In these situations you'll have what is
> called a "Merge effect" - think of it this way, I'm a parent of Triplets
> (honest, age 11) On Saturday morning I say to the kids, hey, lets go
> fishing. When do I actually back out of the garage? When the last kid gets
> into the car not when the average kid gets into the car, not when the kid
> plus one standard deviation gets into the car... Well projects often have
> the same situation multiple critical or near critical paths...
>
> So the only way to get a proper duration calculation is through a monte
> carlo simulation...

If the task is far away of the critical path, so much as to never be in
a critical path, you can pick up an ending time with a 100% probability
of finishing there without any problem.

My situation maybe is more theoretical rather than real, but the case
can happen.

>
> >I used python to do my Monte Carlo simulation program because it already
> >has a package for a lot of probability distributions (scipy).
>
> great I assume we can use these in Planner.
>

Yeah, no problem with that.  Scipy package maybe is quite a problem as a
dependency, because it depends on the numeric package.  I don't know if
it would be easier to create something from scratch (just the
probability distribution CDF for random number generation).

>
> >I really think that it is not hard to do the simulation, but get harder
> >to integrate it visually with all the other things.  Once you have your
> >uncertain durations, you should calculate your uncertain costs ;-)
>
> I have lots of ideas on the visual aspect, even with limited access to MS
> Project's user interface (you can't put graphics on the gantt chart for
> example) I've been able to show the user duration means and standard
> deviations etc.
>

My idea is to show actually the CDF of the starting and ending time.
I'll try to make a picture of something like that.

> Mark
>
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```

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