[Population Modeling] Population modeling definition

Fri Jan 16 02:07:08 PST 2015

Hi Talitha, Hi John, Hi Olaf, Hi Steve, Hi Stephan, Hi Al, and greeting to
all others who have not participated yet.

You have contributed thoughts to this discussion. I would like to point to
two issues I see and add a third issue to the discussion

1. Dictionary like definition:
John and Olaf are trying to define the term like a dictionary. In this
perspective, I myself would interpret population as: "A collection of X"
where X can change as Madhav suggested before. It is probably a noun
describing plurality of X.

2. Definition by Models included:
However, perhaps a more interesting discussion is what kind of models fall
into our category. I recall Al and Steve trying to include Markov models,
while Talitha and previously Stephan are excluding Markov Cohort models
from falling within our definition of population modeling. This is to the
best of my understating and I am surprised that Talitha suggested a strict
definition since she some of her work is Markov model based.

What would you all feel about including Markov models within population
modeling only if they stratify the cohort by age, gender, and/or other
parameters. And non stratified models will define these as cohort models
outside population modeling?

3. Modeling of individual uncertainty
This is another question. Would we consider description of uncertainty of
parameters in an individual within our population modeling group? For
example, does defining distribution of height of a person by mean,
variance, and distribution function fall into our category? After all we
are modeling a single entity from information derived from a population. I
would say yes, especially if the information is extracted from a population
that we can name. But what about correlation between anthropometric
features such as defining the mean ratio between height and arm length as
one number? Will one number be sufficient  to call it population modeling
or do we need a distribution? I would say if the number is associated to a
population cohort then perhaps, and defiantly yes if we have several
numbers associated with different population cohorts.

I am interested to learn more what others think of those questions. I hope
others will join this discussion.

               Jacob

On Tue, Jan 13, 2015 at 3:25 PM, Talitha Feenstra <talitha.feenstra at rivm.nl>
wrote:

> Dear all,
>
> Following up on the definition discussion.
>
> I would suggest that the structure of the model (state transition, or DES,
> or agent-based, or whatever) is not so important for the question whether
> or not a model is a population model.
> More important seems that it reflects a "population". That is, rather than
> simulating a cohort of say 1000 people, it contains information on a
> population's epidemiology and demography. This may or may not include
> birth,and migration, and almost always includes mortality. This would then
> indeed exclude Markov cohort models, but more due to the cohort aspect than
> for their lack of modeling heterogeneity.
>
> However the examples presented go very broad and also include populations
> of animals and even nonliving objects. Especially the latter gets confusing
> to me, how to distinguish between what I knew of as "agent-based modeling"
> which is a model structure, and "population modeling" ?
>
> kind regards, Talitha Feenstra
>
>
> TL Feenstra, PhD
> health economist
> RIVM, Centre for Nutrition, Prevention and Health Services Research
> Po Box 1
> 3720 BA Bilthoven
> *31 30 274 4387 (mon)
> * 31 6 1186 87 60
> UMCG, dept of epidemiology
> PO Box 30.001
> 9700 RB Groningen
> *31 50 361 5110 (tue/thu/fri)
>
> -----popmodwkgrpimag-news-bounces at simtk.org wrote: -----
> To: popmodwkgrpimag-news at simtk.org
> From: Stefan Scholz
> Sent by: popmodwkgrpimag-news-bounces at simtk.org
> Date: 01/07/2015 10:58PM
> Subject: Re: [Population Modeling] Population modeling definition
>
>
> Hello all,
>
> I think the definition hits the broad subject really well. Maybe I am
> seeing too much through the eyes of a health economist, but I would draw
> the line of population models right after (cohort) markov models. In my
> opinion mostly all of those cohort models ignore patient heterogeneity and
> focus more on the disease rather than the population. On the other hand I
> would say that "Individual Sampling Models" and DES as presented by Al
> Chrosny and Jon Karnon do incorporate patient heterogeneity and should be
> presented by the term "population model". So maybe we can draw the line
> between cohort and individual Markov models.
>
> Best regards,
> Stefan
>
>
>
> On 07.01.2015 22:17, 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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