[Population Modeling] Population modeling definition

[Al Chrosny]

Jacob,

I agree that Markov models are most often used for modeling a homogenous 
cohort of entities.

However, it is quite straightforward to introduce heterogeneity to a 
Markov model.  One simple way is to do this is to perform a series of 
individual entity simulations.  Each entity can have different 
characteristics as it enters the Markov model.  The results for all 
entities are then aggregated to present a heterogeneous cohort results.

So different flavors of Markov modelling can included within the 
proposed definition:
"Modeling a collection of entities with different levels of heterogeneity"

Al

On 1/7/2015 4:17 PM, Jacob Barhak wrote:
>
> Hello All,
>
> There is a growing demand to define the term population modeling. This 
> need is visible in some recent personal communications.
>
> This post will try to bring some quotes from different people who try 
> to define it during conversation. I intend to use some of this in the 
> paper, so I am bringing it to the list first to get opinions of more 
> people.
>
> So here are key quotes:
>
> Sergey Nuzhdin USC:
>
> "we are doing lots of population / quantitative modeling, and i would 
> love to get engaged in human community;
>
> but so far, our efforts have been in Drosophila and plants"
>
> John Rice - Society for Simulation in Heathcare (SSiH)  government 
> relations vice chair:
>
> "Sergey,  perfect!  I want to learn about PopMod for non human 
> sciences and engineer applications.  If we had a population of trees 
> in a forrest,  in stead of a generalized collective description. Could 
> we predict the course of a forrest fire better?  Only beginning to 
> think about that, then here you are, modeling a populations of  plants."
>
> Sergey replying:
> " you are right, John, precisely what we are doing (among other things);
>
> how to predict collective properties from individual ones;
>
> there is plenty done about it when the subjects are homogeneous, and 
> very little when heterogeneous;"
>
> Madhav Marathe - Virginia Tech:
> "The population modeling group is intended to be broad. Ofcourse 
> making it way too broad might make it harder for a cohesive 
> conversation but we can see how it plays out. I am calling this 
> population of things; it appears things is the best word I can use to 
> keep the intended generality. We have studied cells, wireless devices, 
> people and animals in the past for instance."
>
> It seems that the above discussion matches the ad hoc definition we 
> reached at the IMAG meeting at the NIH:
>
> "Modeling a collection of entities with different levels of heterogeneity"
>
> We reached this definition quickly and it was a broad consensus. 
> However, others on the list may want to discuss this definition and 
> offer alternatives.
>
> For example Markov models address populations mostly as time series 
> and seldom consider differences between individual entities,  yet I 
> would still include Markov models under the umbrella of population 
> modeling. It is a difficult fit to the above definition unless 
> hetrogeneity among states is considered within time.
>
> I would appreciate your thoughts and will try to incorporate those in 
> the paper.
>
>           Jacob
>
>
>
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-- 
Wojciech (Al) Chrosny, Ph.D.
Director Software Engineering
TreeAge Software, Inc.
+1.413.241.3225

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