How to measure porject duration?

[xhoward]

Hi,

I'm currently working on a SD model of product development.
Inspired by "Dynamic Modeling of Product Development" (Ford, 1998), I build my own model and use a variable named "%Tasks Done" to observe project duration.
For example, if "%Tasks Done" reaches 100% in the 90th day, the project duration will be 90days.

However, as I want to do further sensitivity analysis with hundreds of simulation runs, I find that I cannot count the statistics of project duration in the context. So I want to design a variable named "Project Duration," which aims to
record the "Xth" day when taks are 100% done. So that I can count the statistics, i.e. mean, standard deviation, etc., of project duration after hundreds of runs.

I have tried different ways but hardly make the ideas work.
Can anyone tell me how to achieve above-goals?
I would appreciate any available suggestions from you.

Howard

[Edited on 4-8-2008 by xhoward]

[Edited on 4-8-2008 by xhoward]

[bob@vensim.com]

A simple formulation for project duration would be

project duration = INTEG(IF THEN ELSE(project is finished,0,1),0)

[xhoward]

Dr. Bob,

Thank you very much for your advice.

It's so stupid that I didn't use the level.
Instead, I marked "project duration" as a variable in which
"Time" (unit:day) accumulates, i.e. ++, until project is done.
Iappropriate trials get me into a blind alley...

Howard

Originally posted by bob@vensim.com
A simple formulation for project duration would be

project duration = INTEG(IF THEN ELSE(project is finished,0,1),0)