REPLY Meaning of Stock/Level (SD6913)

[SDMAIL Jim Thompson]

Posted by  Jim Thompson <james.thompson at strath.ac.uk>

My reaction to the original query and some responses is similar
to Bob Eberlein's response of 11 April, and prompts me to add a
couple of thoughts.

When Bob and others refer to "models containing these types of
variables", we mean that there are feedbacks from soft variables
that affect system behaviour.  To include a variable means that
the modeller thinks it represents part of his experience.

Variables such as 'trust' and 'morale' often reflect measurable
experiences.  For example, 'trust' can reflect 'promises kept',
and one can measure promises made, kept and broken...at least in
theory.  Morale may be partly a function of actual performance
versus expected performance, and these too can be measured.

As Bob pointed out, not everything that affects a system can be
measured directly and not everything that can be measured
directly affects the system. One contribution of system dynamics
methodology is finding out what matters.
Jim Thompson
Posted by  Jim Thompson <james.thompson at strath.ac.uk>
posting date  Fri, 11 Apr 2008 12:03:14 -0400