<div dir="ltr"><p class="MsoNormal"><span style="background-image:initial;background-repeat:initial">Talitha, <a href="http://et.al">et.al</a>.,</span></p>
<p class="MsoNormal"><span style="background-image:initial;background-repeat:initial"> </span></p>
<p class="">As a naive observer I willingly accept the risk of asking
questions or making suggestions that may not be of interest or even
relevant. That said.</p>
<p class="MsoNormal"><span style="background-image:initial;background-repeat:initial"> </span></p>
<p class="MsoNormal"><span style="background-image:initial;background-repeat:initial">1. WRT to non living “populations”:</span></p>
<p class="MsoNormal"><span style="background-image:initial;background-repeat:initial">Think about guardrails on the
interstate. There are thousands of
metal I-beams sunk into the ground to be the posts to which the rails are
attached. I suspect that engineers did
models to determine the characteristics of the material of which they are made,
their shape, size and and implantation.
In their models they looked at objects of given mass, and shape moving
at some velocity striking the rail to determine an optimal design including the
composition of beams themselves, where to drill holes to attach the rails, how
to set them in the ground, etc., all based on an assumption that all of the
beam were identical for all know and measurable (hopefully) parameters. They run the models and determine that the
rail SYSTEM will absorb some amount of energy which would prevent the moving
object from impacting a tree head on, while also not being just another
“TREE”. But…. Even among 10, 6-foot rail posts cut from
the same 60ft beam; there are metallurgical differences and/or other flaws that
could affect performance of each individual post. (Hopefully small, but each
post will be different to a degree dependent on the quality control.) After cut
to post length, the holes are drilled for the bolts to attach the rail, (pretty
precise but not perfect) and each is eventually anchored in the ground one at a
time. Thus each post-system is a bit different, and in some there may be
significant differences (flaws) not found because the quality assurance testing
also assumes that for all practical purposes the entire 60-ft beam from which
they were cut is the same. So the
question is, what might we learn from running the crash models with a model in
which each post system (including the quite variable way it was set into the
ground were modeled individually using "population” (adjective) modeling.
I want to answer the question, ‘what is the likelihood of a post system not
yielding as the design intends thus becoming a ‘tree’ that kills the family
instead of a shock absorber. I suspect
that would fit as population modeling. ?????</span></p>
<p class="MsoNormal"><span style="background-image:initial;background-repeat:initial"> </span></p>
<p class="MsoNormal"><span style="background-image:initial;background-repeat:initial">2. Not to overdo the adjective (maybe
adverb) vs. noun thing but…. The noun
answer to me is what I would expect from a layperson reading only the headline
and first sentence of a newspaper article on population modeling. (You guys are picking the term and there are
downsides to labeling a new construct of any kind with a couple commonly used
words.) But Olaf’s short answer
“noun”, presumably naming the object of the modeling did surprise me a
little. So this naive observers thinks
that now I do not understand even though I asked the question. I agree that linguistically his answer makes
perfect sense but it raised the following:
it suggests that ‘population modeling’ is nothing new. Social scientist
with out math mentally modeled “populations’ to write books or at least
described population behavior maybe before numbers existed and have done a lot
of work modeling the behavior of “populations = groups” of people described as
having and/or not having certain measurable (I hope) characteristic that
qualified them as a member of a group defined by those characteristics, or a
non-member. And then they did that with
mathematical models using paper and slide rules and 10 key calculators. So yes, I would call that “population
modeling”. However, I was attracted to
observe the emergence of this population modeling group by people who do what I
think most IMAG people do, i.e. use “high performance” computational tools to
increase the degree of detail possible for building models.</span><span style="font-size:10pt;font-family:Arial;background-image:initial;background-repeat:initial"></span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">Now my question is, is there some level of granularity
characteristic within the construct of population modeling that makes the
modeling of a population DOING ‘population (adverb/adverb) modeling as
different than what can be done with ‘common’ vs. HP computational
methods/tools? If so, there may be some
risk of calling the KIND of modeling you (collectively for now) are calling
population (a common word) modeling which could be misinterpreted as the
objects of the model when (if) you are really wanting to bound the description
of a METHOD(S) for modeling. </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">NEW TOPIC (sort of) If there really is no documented
‘definition’ to describe PopMod and distinguish it from non PopMod modeling,
those coming forward in response to this call for PopMod’ers who believing that
whatever they are doing is an example will be the ones to define for
posterity. To protect your concept of
the construct from abuse (which could give it a bad name someday), your
description (subject to evolutionary expansion over the years) will need to be
clear. </p>
<p class="MsoNormal">
</p>
<p class="MsoNormal">As a not quiet so naive cognitive science type, I suggest
you consider the following: to be useful an indiviual’s concept of a named
construct must allow them to determine whether or not any potential
instantiation of the construct is or is not an example of the original
construct. In the instructional design
world we teach concepts by presenting example and ‘non examples’. The degree of refinement at the margins
between the example which are included in the construct and the non-example
which may on the surface appear to be within, but are actually not example of,
in this case the construct population modeling. So consider finding some real, and/or creating some hypothetical
examples and non-examples of “population models” (5-6 of each) with relatively
simple one paragraph descriptions and putting them into the example or
non-example baskets. Some kind of descriptive format for the exemplar models
that provided a way to briefly address characteristics that are most
germane to classifying them as examples or non-examples would be very helpful
both to your own thinking about what distinguish PopMods from other kinds of
models and for sharing the examples with others in ‘elevator speech’ time. Play with them. Move them around modify them, think about what might justify
changing which basket they belong in; and when you have some general agreement,
use the experience to write a 1-2 paragraph description of what PopMod is. Send the description to me and send me the
10-12 one-paragraph descriptions of the
models from the example, non-example baskets in random order to see if,after I
read you description of the construct PopMod, I can place each example of a
model inscriptions into the correct PopMod or Non PopMod basket. If I can come pretty close I will be happy
to pass the exercise along to some of my quite more sophisticated M&S
friend as an exercise followed by solicitation of their questions or
suggestions. </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">John</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">. </p></div><div class="gmail_extra"><br><div class="gmail_quote">On Sat, Jan 17, 2015 at 5:06 AM, <span dir="ltr"><<a href="mailto:popmodwkgrpimag-news-request@simtk.org" target="_blank">popmodwkgrpimag-news-request@simtk.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Send PopModWkGrpIMAG-news mailing list submissions to<br>
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Today's Topics:<br>
<br>
1. Re: Population modeling definition (Jacob Barhak)<br>
<br>
<br>
----------------------------------------------------------------------<br>
<br>
Message: 1<br>
Date: Fri, 16 Jan 2015 04:07:08 -0600<br>
From: Jacob Barhak <<a href="mailto:jacob.barhak@gmail.com">jacob.barhak@gmail.com</a>><br>
Subject: Re: [Population Modeling] Population modeling definition<br>
To: Talitha Feenstra <<a href="mailto:talitha.feenstra@rivm.nl">talitha.feenstra@rivm.nl</a>><br>
Cc: <a href="mailto:popmodwkgrpimag-news@simtk.org">popmodwkgrpimag-news@simtk.org</a><br>
Message-ID:<br>
<CAM_y+3S_D1e1GhKA_8C8zvTeijA2_3nEupq61Jx1h-=<a href="mailto:s6mmGAA@mail.gmail.com">s6mmGAA@mail.gmail.com</a>><br>
Content-Type: text/plain; charset="utf-8"<br>
<br>
Hi Talitha, Hi John, Hi Olaf, Hi Steve, Hi Stephan, Hi Al, and greeting to<br>
all others who have not participated yet.<br>
<br>
You have contributed thoughts to this discussion. I would like to point to<br>
two issues I see and add a third issue to the discussion<br>
<br>
1. Dictionary like definition:<br>
John and Olaf are trying to define the term like a dictionary. In this<br>
perspective, I myself would interpret population as: "A collection of X"<br>
where X can change as Madhav suggested before. It is probably a noun<br>
describing plurality of X.<br>
<br>
2. Definition by Models included:<br>
However, perhaps a more interesting discussion is what kind of models fall<br>
into our category. I recall Al and Steve trying to include Markov models,<br>
while Talitha and previously Stephan are excluding Markov Cohort models<br>
from falling within our definition of population modeling. This is to the<br>
best of my understating and I am surprised that Talitha suggested a strict<br>
definition since she some of her work is Markov model based.<br>
<br>
What would you all feel about including Markov models within population<br>
modeling only if they stratify the cohort by age, gender, and/or other<br>
parameters. And non stratified models will define these as cohort models<br>
outside population modeling?<br>
<br>
3. Modeling of individual uncertainty<br>
This is another question. Would we consider description of uncertainty of<br>
parameters in an individual within our population modeling group? For<br>
example, does defining distribution of height of a person by mean,<br>
variance, and distribution function fall into our category? After all we<br>
are modeling a single entity from information derived from a population. I<br>
would say yes, especially if the information is extracted from a population<br>
that we can name. But what about correlation between anthropometric<br>
features such as defining the mean ratio between height and arm length as<br>
one number? Will one number be sufficient to call it population modeling<br>
or do we need a distribution? I would say if the number is associated to a<br>
population cohort then perhaps, and defiantly yes if we have several<br>
numbers associated with different population cohorts.<br>
<br>
I am interested to learn more what others think of those questions. I hope<br>
others will join this discussion.<br>
<br>
Jacob<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
On Tue, Jan 13, 2015 at 3:25 PM, Talitha Feenstra <<a href="mailto:talitha.feenstra@rivm.nl">talitha.feenstra@rivm.nl</a>><br>
wrote:<br>
<br>
> Dear all,<br>
><br>
> Following up on the definition discussion.<br>
><br>
> I would suggest that the structure of the model (state transition, or DES,<br>
> or agent-based, or whatever) is not so important for the question whether<br>
> or not a model is a population model.<br>
> More important seems that it reflects a "population". That is, rather than<br>
> simulating a cohort of say 1000 people, it contains information on a<br>
> population's epidemiology and demography. This may or may not include<br>
> birth,and migration, and almost always includes mortality. This would then<br>
> indeed exclude Markov cohort models, but more due to the cohort aspect than<br>
> for their lack of modeling heterogeneity.<br>
><br>
> However the examples presented go very broad and also include populations<br>
> of animals and even nonliving objects. Especially the latter gets confusing<br>
> to me, how to distinguish between what I knew of as "agent-based modeling"<br>
> which is a model structure, and "population modeling" ?<br>
><br>
> kind regards, Talitha Feenstra<br>
><br>
><br>
> TL Feenstra, PhD<br>
> health economist<br>
> RIVM, Centre for Nutrition, Prevention and Health Services Research<br>
> Po Box 1<br>
> 3720 BA Bilthoven<br>
> *31 30 274 4387 (mon)<br>
> * 31 6 1186 87 60<br>
> UMCG, dept of epidemiology<br>
> PO Box 30.001<br>
> 9700 RB Groningen<br>
> *31 50 361 5110 (tue/thu/fri)<br>
><br>
> -----<a href="mailto:popmodwkgrpimag-news-bounces@simtk.org">popmodwkgrpimag-news-bounces@simtk.org</a> wrote: -----<br>
> To: <a href="mailto:popmodwkgrpimag-news@simtk.org">popmodwkgrpimag-news@simtk.org</a><br>
> From: Stefan Scholz<br>
> Sent by: <a href="mailto:popmodwkgrpimag-news-bounces@simtk.org">popmodwkgrpimag-news-bounces@simtk.org</a><br>
> Date: 01/07/2015 10:58PM<br>
> Subject: Re: [Population Modeling] Population modeling definition<br>
><br>
><br>
> Hello all,<br>
><br>
> I think the definition hits the broad subject really well. Maybe I am<br>
> seeing too much through the eyes of a health economist, but I would draw<br>
> the line of population models right after (cohort) markov models. In my<br>
> opinion mostly all of those cohort models ignore patient heterogeneity and<br>
> focus more on the disease rather than the population. On the other hand I<br>
> would say that "Individual Sampling Models" and DES as presented by Al<br>
> Chrosny and Jon Karnon do incorporate patient heterogeneity and should be<br>
> presented by the term "population model". So maybe we can draw the line<br>
> between cohort and individual Markov models.<br>
><br>
> Best regards,<br>
> Stefan<br>
><br>
><br>
><br>
> On 07.01.2015 22:17, Jacob Barhak wrote:<br>
><br>
> Hello All,<br>
><br>
> There is a growing demand to define the term population modeling. This<br>
> need is visible in some recent personal communications.<br>
><br>
> This post will try to bring some quotes from different people who try to<br>
> define it during conversation. I intend to use some of this in the paper,<br>
> so I am bringing it to the list first to get opinions of more people.<br>
><br>
> So here are key quotes:<br>
><br>
> Sergey Nuzhdin USC:<br>
><br>
> "we are doing lots of population / quantitative modeling, and i would love<br>
> to get engaged in human community;<br>
><br>
> but so far, our efforts have been in Drosophila and plants"<br>
><br>
> John Rice - Society for Simulation in Heathcare (SSiH) government<br>
> relations vice chair:<br>
><br>
> "Sergey, perfect! I want to learn about PopMod for non human sciences<br>
> and engineer applications. If we had a population of trees in a forrest,<br>
> in stead of a generalized collective description. Could we predict the<br>
> course of a forrest fire better? Only beginning to think about that, then<br>
> here you are, modeling a populations of plants."<br>
><br>
> Sergey replying:<br>
> " you are right, John, precisely what we are doing (among other things);<br>
><br>
> how to predict collective properties from individual ones;<br>
><br>
> there is plenty done about it when the subjects are homogeneous, and very<br>
> little when heterogeneous;"<br>
><br>
> Madhav Marathe - Virginia Tech:<br>
> "The population modeling group is intended to be broad. Ofcourse making it<br>
> way too broad might make it harder for a cohesive conversation but we can<br>
> see how it plays out. I am calling this population of things; it appears<br>
> things is the best word I can use to keep the intended generality. We have<br>
> studied cells, wireless devices, people and animals in the past for<br>
> instance."<br>
><br>
> It seems that the above discussion matches the ad hoc definition we<br>
> reached at the IMAG meeting at the NIH:<br>
><br>
> "Modeling a collection of entities with different levels of heterogeneity"<br>
><br>
> We reached this definition quickly and it was a broad consensus.<br>
> However, others on the list may want to discuss this definition and offer<br>
> alternatives.<br>
><br>
> For example Markov models address populations mostly as time series and<br>
> seldom consider differences between individual entities, yet I would still<br>
> include Markov models under the umbrella of population modeling. It is a<br>
> difficult fit to the above definition unless hetrogeneity among states is<br>
> considered within time.<br>
><br>
> I would appreciate your thoughts and will try to incorporate those in the<br>
> paper.<br>
><br>
> Jacob<br>
><br>
><br>
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End of PopModWkGrpIMAG-news Digest, Vol 3, Issue 17<br>
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<br>
</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature">“Where there is much desire to learn, here of necessity will be much arguing, <br>much writing, many opinions; for opinion in good men is but knowledge in the making.”<br>John Milton (1608 – 1674)<br><br>Cellular 757 318 0671<br></div>
</div>