Subject: Connections between models and reality

Posted by Steve Kipp on 3/11/2004
In Reply To:Connections between models and reality Posted by John Gunkler on 3/10/2004

Message:

John- Thanks for your clear explanation of how it is impossible to instantaneously measure any flow, I had been puzzled by Mohamad’s post, but it makes sense to me now: all measured rates are averages over some period of time, therefore impossible to measure directly. My skill and knowledge of the intricacies of System Dynamics takes a little tick upward! But I still don’t want to have to explain that to middle school language arts teachers, nor do I think it would help them to help their students better understand their world if I tried, given limited “commons” of human time and attention. So I look in the mirror and include myself when I say- just because we get nerdly joy from learning such counterintuitive truths, doesn’t mean we should try to teach that to everybody, but everybody can benefit tremendously from increasing their conceptual understanding of stocks and flows at some level, in contexts that speak to them personally. Does that makes sense?



I have run into a situation where the true instantaneous nature of flows might increase clarity, though: I will sometimes have a student predict that a graph of a Bank Account stock with Interest Payments inflow will jump up in little stair-steps, and I have lamely said in the past “well, you’re right, because each deposit is a discreet event, but the computer just draws the line that way”. Now I’ll be able to give a bit more of an explanation in this situation.

Only when solicited, though, and if I can do it without killing the momentum of the lesson...the overall behavior of the system is usually what we are after.



Steve

Follow Ups:

Connections between models and reality - Mohamad Morovati 3/11/2004