REPLY Ensuring Quality of Models (SD6661)

[SDMAIL Kim Warren]

Posted by  "Kim Warren" <Kim at strategydynamics.com>

A small tip, but one I have found immensely useful I believe should be
credited to Geoff Coyle .. A model should do what the real world does,
and for the same reasons.

The first clause hits the 'goodness of fit' criterion, but the second
has two further implications. First, the model should only include
elements that can be identified and measured [or conceivably could be]
in the real world. Secondly, those real-world variables should also
behave as observed.

As I understand it, the major risk if this additional consideration is
not included is that a model may fit well with historical data, but then
immediately go off-track as soon as the future starts to unfold.
Additional problems include the significant issue of getting management
to buy in to a model in which they don't recognise the elements of which
it is made up. 

There is a puzzle in all this, though. Many of the most insightful SD
models are simplified to high levels of abstraction. Yet skilled SD-ers
somehow manage to generate confidence in the structure and findings.
This seems an important skill, as it is often not practical to capture
enough real-world detail to fully conform to the rule above. I may not
be alone in welcoming advice on how to accomplish this.

Kim Warren
Posted by  "Kim Warren" <Kim at strategydynamics.com>
posting date  Mon, 12 Nov 2007 10:17:55 -0000