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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">Re: Definition<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">This may be too late for the paper, but here is my 2 cents.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">I think it is important to distinguish between system of care population models and epidemiological or etiological population models (as I understand them from
 discussions on this list).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">Epidemiological or etiological population models (and I may not have this right, since I do not do this type of modeling) seem to focus on the causes and distributions
 of illnesses or other things in populations.&nbsp; It seems to me that these models usually assume a system of care – something like treatment as usual, although this is not always made explicit, although I think models are more useful if the nature of the care
 available is made explicit.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">Systems of care population models focus on distributions of persons in systems of care, usually categorized according to health or service states (more on that
 in a moment) and how persons move or transition through theses states as a function of the type of service they receive and their characteristics or the course of their disorder.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">Re: Jacob’s comment below:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal" style="margin-left:1.0in"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">For example Markov models address populations mostly as time series and seldom consider differences between individual entities,&nbsp;
 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.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:1.0in"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">I’m not sure I understand this, but I would say Markov models commonly consider differences between individual entities, if what is meant by “differences” is
 differences in health states.&nbsp; Moreover, different Markov models can be constructed for different populations distinguished by things like diagnoses, then their results can be combined to model more complex populations.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">One more point: Although systems of care often use as health states locations in particular services (e.g., inpatient care), I think the most useful systems
 of care models use health states based on epidemiological categories (to muddy the waters a bit) such as “acutely disturbed,” “mildly disturbed,” and so on.&nbsp; When we use service locations we confound health states with the services available in systems.&nbsp; So
 in mental health systems higher functioning persons can be in hospitals because community residential care is not available, not because their heath states warrant inpatient care.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:1.0in"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">Anyway, the discussions on the list have been very thought provoking.&nbsp; Thanks, everyone.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">Virtually,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D">Steve Leff<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:&quot;Calibri&quot;,&quot;sans-serif&quot;;color:#1F497D"><o:p>&nbsp;</o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:&quot;Tahoma&quot;,&quot;sans-serif&quot;">From:</span></b><span style="font-size:10.0pt;font-family:&quot;Tahoma&quot;,&quot;sans-serif&quot;"> popmodwkgrpimag-news-bounces@simtk.org [mailto:popmodwkgrpimag-news-bounces@simtk.org]
<b>On Behalf Of </b>Jacob Barhak<br>
<b>Sent:</b> Wednesday, January 07, 2015 4:18 PM<br>
<b>To:</b> popmodwkgrpimag-news@simtk.org<br>
<b>Subject:</b> [Population Modeling] Population modeling definition<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p>&nbsp;</o:p></p>
<p>Hello All,<o:p></o:p></p>
<p>There is a growing demand to define the term population modeling. This need is visible in some recent personal communications.<o:p></o:p></p>
<p>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.<o:p></o:p></p>
<p>So here are key quotes:<o:p></o:p></p>
<p>Sergey Nuzhdin USC:<o:p></o:p></p>
<p>&quot;we are doing lots of population / quantitative modeling, and i would love to get engaged in human community;<o:p></o:p></p>
<p>but so far, our efforts have been in Drosophila and plants&quot;<o:p></o:p></p>
<p>John Rice - Society for Simulation in Heathcare (SSiH)&nbsp; government relations vice chair:<o:p></o:p></p>
<p>&quot;Sergey,&nbsp; perfect!&nbsp; I want to learn about PopMod for non human sciences and engineer applications.&nbsp; If we had a population of trees in a forrest,&nbsp; in stead of a generalized collective description. Could we predict the course of a forrest fire better?&nbsp; Only
 beginning to think about that, then here you are, modeling a populations of&nbsp; plants.&quot;<o:p></o:p></p>
<p>Sergey replying: <br>
&quot; you are right, John, precisely what we are doing (among other things);<o:p></o:p></p>
<p>how to predict collective properties from individual ones;<o:p></o:p></p>
<p>there is plenty done about it when the subjects are homogeneous, and very little when heterogeneous;&quot;<o:p></o:p></p>
<p>Madhav Marathe - Virginia Tech: <br>
&quot;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.&quot;<o:p></o:p></p>
<p>It seems that the above discussion matches the ad hoc definition we reached at the IMAG meeting at the NIH:<o:p></o:p></p>
<p>&quot;Modeling a collection of entities with different levels of heterogeneity&quot;<o:p></o:p></p>
<p>We reached this definition quickly and it was a broad consensus. However,&nbsp;others on the list may want to discuss this definition and offer alternatives.<o:p></o:p></p>
<p>For example Markov models address populations mostly as time series and seldom consider differences between individual entities,&nbsp; 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.<o:p></o:p></p>
<p>I would appreciate your thoughts and will try to incorporate those in the paper.<o:p></o:p></p>
<p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Jacob<o:p></o:p></p>
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