REPLY Meaning of Stock/Level (SD6908)

[SDMAIL Malli]

Posted by  "Malli" <malli at madisonindia.com>

I have been studying system dynamics for the last 2 years, and have been 
following this discussion on qualitative variables with great interest. 
The fact that system dynamics as a modeling worldview allows the modeler 
to incorporate both measured variables as well as those that are not 
measured is what attracted me to this field. However, while quantifying 
a soft variable such as morale, should one also think about the scale? 
Essentially, is one referring to the variable using an interval scale or 
a ratio scale? As one knows, on the interval scale, the zero is 
arbitrary - If the temperature today is 100 degrees Fahrenheit, and 
yesterday it was 50 degrees Fahrenheit, then one cannot say that today 
is twice as hot as yesterday.

On the other hand, if one is using a ratio scale, then such statements 
can be asserted. A market share of 20% is twice that of 10%

While quantifying soft variables, such as morale, if the morale dips 
from 100 to 98, then what is the scale that one is referring to? Should 
I be alarmed or not? If the body temperature increases from 98.5 Degrees 
F to 102 Degrees F, I definitely am! however, seen from a ratio scale 
this increment would be a small blip!

This is one aspect that has always puzzled me about the quantification 
of soft variables

Malli
Posted by  "Malli" <malli at madisonindia.com>
posting date  Fri, 11 Apr 2008 17:46:45 -0700