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	<title>Comments on: Sunday Morning Reading</title>
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		<title>By: mod converter</title>
		<link>http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html/comment-page-1#comment-24881</link>
		<dc:creator>mod converter</dc:creator>
		<pubDate>Tue, 16 Mar 2010 02:54:35 +0000</pubDate>
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		<description>This article is very interesting. Thank you very much for sharing .    </description>
		<content:encoded><![CDATA[<p>This article is very interesting. Thank you very much for sharing .</p>
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		<title>By: sigmawaite</title>
		<link>http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html/comment-page-1#comment-11786</link>
		<dc:creator>sigmawaite</dc:creator>
		<pubDate>Sun, 22 Mar 2009 23:52:06 +0000</pubDate>
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		<description>Yes, &quot;social science research&quot; has some challenges.  My wife and brother tried, but I stayed with math, physical science, engineering, and technology (for business). 
 
But the two problems we have mentioned, that some people forgot that (1) &quot;We found there is no benefit ...&quot; is not the same as there was no benefit and (2) the central limit theorem does not guarantee to kill black swans, are elementary mistakes and more an embarrassment of some social scientists than the challenges of social science problems. 
 
Is it possible to make progress in the social sciences?  Actually, yes:  For (1), that is just a hypothesis test, and the social sciences have long commonly made good use of that subject, e.g., as in 
 
Sidney Siegel, &#039;Nonparametric Statistics for the Behavioral Sciences&#039;, McGraw-Hill, New York, 1956. 
 
Some people in the social sciences know this material well.  The system monitoring communities in computer science and information technology would do well getting caught up on such material. 
 
For more, the recent rapid progress in &#039;social&#039; applications of computing and the Internet show progress in understanding &#039;social&#039; phenomena. 
 
Having the social sciences as precise as mathematical physics soon?  No.  Possible to make progress in the social sciences?  Yes. 
 </description>
		<content:encoded><![CDATA[<p>Yes, &quot;social science research&quot; has some challenges.  My wife and brother tried, but I stayed with math, physical science, engineering, and technology (for business). </p>
<p>But the two problems we have mentioned, that some people forgot that (1) &quot;We found there is no benefit &#8230;&quot; is not the same as there was no benefit and (2) the central limit theorem does not guarantee to kill black swans, are elementary mistakes and more an embarrassment of some social scientists than the challenges of social science problems. </p>
<p>Is it possible to make progress in the social sciences?  Actually, yes:  For (1), that is just a hypothesis test, and the social sciences have long commonly made good use of that subject, e.g., as in </p>
<p>Sidney Siegel, &#039;Nonparametric Statistics for the Behavioral Sciences&#039;, McGraw-Hill, New York, 1956. </p>
<p>Some people in the social sciences know this material well.  The system monitoring communities in computer science and information technology would do well getting caught up on such material. </p>
<p>For more, the recent rapid progress in &#039;social&#039; applications of computing and the Internet show progress in understanding &#039;social&#039; phenomena. </p>
<p>Having the social sciences as precise as mathematical physics soon?  No.  Possible to make progress in the social sciences?  Yes.</p>
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		<title>By: Eric von Hippel</title>
		<link>http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html/comment-page-1#comment-11781</link>
		<dc:creator>Eric von Hippel</dc:creator>
		<pubDate>Sun, 22 Mar 2009 21:50:34 +0000</pubDate>
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		<description>Well, that&#039;s what they mean by the &quot;doctor father&quot; role - if I do it right we both grow - and end up with a life-time bond! </description>
		<content:encoded><![CDATA[<p>Well, that&#039;s what they mean by the &quot;doctor father&quot; role &#8211; if I do it right we both grow &#8211; and end up with a life-time bond!</p>
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		<title>By: bfeld</title>
		<link>http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html/comment-page-1#comment-11780</link>
		<dc:creator>bfeld</dc:creator>
		<pubDate>Sun, 22 Mar 2009 21:21:07 +0000</pubDate>
		<guid isPermaLink="false">http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html#comment-11780</guid>
		<description>Yeah,  well, who knows!  I recall formally taking an “indefinite leave of absence” but  in the context of “get serious about this or take an indefinite leave of  absence.”  By the time the moment of truth about getting serious about it came,  I was way more interested in the companies I was involved in than in the actual  PhD activity.  Regardless  of whether I was “kicked out”, “left because I lost interest”, or “some other  dynamic”, the experience was hugely important to me on many levels, as was your  involvement and mentoring.  I clearly recall you giving me plenty of time and  space to figure out what I wanted to do and being supportive regardless of  which path I took.  If nothing else (and I learned loads of other things),  learning the value of that was a biggie!  </description>
		<content:encoded><![CDATA[<p>Yeah,  well, who knows!  I recall formally taking an “indefinite leave of absence” but  in the context of “get serious about this or take an indefinite leave of  absence.”  By the time the moment of truth about getting serious about it came,  I was way more interested in the companies I was involved in than in the actual  PhD activity.  Regardless  of whether I was “kicked out”, “left because I lost interest”, or “some other  dynamic”, the experience was hugely important to me on many levels, as was your  involvement and mentoring.  I clearly recall you giving me plenty of time and  space to figure out what I wanted to do and being supportive regardless of  which path I took.  If nothing else (and I learned loads of other things),  learning the value of that was a biggie!</p>
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		<title>By: Brad Feld</title>
		<link>http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html/comment-page-1#comment-11779</link>
		<dc:creator>Brad Feld</dc:creator>
		<pubDate>Sun, 22 Mar 2009 21:13:28 +0000</pubDate>
		<guid isPermaLink="false">http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html#comment-11779</guid>
		<description>I wasn&#039;t suggesting they were the same problem.  I was suggesting that two different categories of problems confound social science research in similar (yet different) ways. </description>
		<content:encoded><![CDATA[<p>I wasn&#039;t suggesting they were the same problem.  I was suggesting that two different categories of problems confound social science research in similar (yet different) ways.</p>
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		<title>By: Eric von Hippel</title>
		<link>http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html/comment-page-1#comment-11778</link>
		<dc:creator>Eric von Hippel</dc:creator>
		<pubDate>Sun, 22 Mar 2009 20:54:44 +0000</pubDate>
		<guid isPermaLink="false">http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html#comment-11778</guid>
		<description>Actually, as far as I remember, Brad didn&#039;t get kicked out of the PhD program - am I wrong, Brad?  My recollection is that, while a student, he just kept starting new and interesting companies that kept on succeeding and growing.  They took up more and more of his time, and made finishing a PhD less and less interesting to him.  
 
Who knows?  One of these days he might decide to give up his day job and come back and finish up his dissertation.  Could happen.  :) </description>
		<content:encoded><![CDATA[<p>Actually, as far as I remember, Brad didn&#039;t get kicked out of the PhD program &#8211; am I wrong, Brad?  My recollection is that, while a student, he just kept starting new and interesting companies that kept on succeeding and growing.  They took up more and more of his time, and made finishing a PhD less and less interesting to him.  </p>
<p>Who knows?  One of these days he might decide to give up his day job and come back and finish up his dissertation.  Could happen.  <img src='http://www.feld.com/wp/wp-includes/images/smilies/icon_smile.gif' alt=':)' class='wp-smiley' /> </p>
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		<title>By: sigmawaite</title>
		<link>http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html/comment-page-1#comment-11777</link>
		<dc:creator>sigmawaite</dc:creator>
		<pubDate>Sun, 22 Mar 2009 19:58:30 +0000</pubDate>
		<guid isPermaLink="false">http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html#comment-11777</guid>
		<description>The &#039;black swan&#039; problem is different: 
 
Here is how one of the basic arguments in &#039;mathematical finance&#039; went: 
 
We assume that there is no free money, no free lunch, that is, no &#039;arbitrage&#039; because if there were too quickly too many investors would exploit it at which time the arbitrage would no longer exist.  So, this assumption of no arbitrage is, maybe, an okay (for some purposes) first cut assumption for how the market works in the large (even if individual traders get rich with individual stocks).  So, what is left is that no one knows, or has any way of discovering, what the stock market will do tomorrow, the next day, etc.  So, what the market does each day is (something like flipping a coin) probabilistically independent of the past.  Next, lacking any information to the contrary (e.g., no &#039;Monday effect&#039;), we assume that the distribution of the change from one day to the next is always the same.  Soooooo, with these two assumptions, and a relatively mild assumption about the nature of the distribution (finite variance is enough and the Lindeberg-Feller result has a tricky weaker assumption) the change in the stock market over, say, 30 days is the sum of 30 changes each of which is independent and has the same distribution so that by the classic central limit theorem the change over the 30 days must start to be approximated by a Gaussian distribution. 
 
Now, with these assumptions, as the number of days, the 30, grows, the actual distribution will converge to a Gaussian distribution as closely as we please. 
 
In particular, if we look at where the market is, say, each 30 days, then what we get will look, just to the eye, something like Brownian motion. 
 
My view is that this argument (really just the assumptions since the mathematics itself is rock solid) is neither completely wrong nor as accurate as is important. 
 
Even if really believe this argument, (and many traders, e.g., naked short sellers, have reason to laugh) we still do not know how accurately the convergence is to a Gaussian distribution.  In particular, even we add up the daily incremental changes for a year, say, 250 trading days, we still can&#039;t rule out some rare events far out in the tail, that is, a &#039;black swan&#039;. 
 </description>
		<content:encoded><![CDATA[<p>The &#039;black swan&#039; problem is different: </p>
<p>Here is how one of the basic arguments in &#039;mathematical finance&#039; went: </p>
<p>We assume that there is no free money, no free lunch, that is, no &#039;arbitrage&#039; because if there were too quickly too many investors would exploit it at which time the arbitrage would no longer exist.  So, this assumption of no arbitrage is, maybe, an okay (for some purposes) first cut assumption for how the market works in the large (even if individual traders get rich with individual stocks).  So, what is left is that no one knows, or has any way of discovering, what the stock market will do tomorrow, the next day, etc.  So, what the market does each day is (something like flipping a coin) probabilistically independent of the past.  Next, lacking any information to the contrary (e.g., no &#039;Monday effect&#039;), we assume that the distribution of the change from one day to the next is always the same.  Soooooo, with these two assumptions, and a relatively mild assumption about the nature of the distribution (finite variance is enough and the Lindeberg-Feller result has a tricky weaker assumption) the change in the stock market over, say, 30 days is the sum of 30 changes each of which is independent and has the same distribution so that by the classic central limit theorem the change over the 30 days must start to be approximated by a Gaussian distribution. </p>
<p>Now, with these assumptions, as the number of days, the 30, grows, the actual distribution will converge to a Gaussian distribution as closely as we please. </p>
<p>In particular, if we look at where the market is, say, each 30 days, then what we get will look, just to the eye, something like Brownian motion. </p>
<p>My view is that this argument (really just the assumptions since the mathematics itself is rock solid) is neither completely wrong nor as accurate as is important. </p>
<p>Even if really believe this argument, (and many traders, e.g., naked short sellers, have reason to laugh) we still do not know how accurately the convergence is to a Gaussian distribution.  In particular, even we add up the daily incremental changes for a year, say, 250 trading days, we still can&#039;t rule out some rare events far out in the tail, that is, a &#039;black swan&#039;.</p>
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		<title>By: Brad Feld</title>
		<link>http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html/comment-page-1#comment-11774</link>
		<dc:creator>Brad Feld</dc:creator>
		<pubDate>Sun, 22 Mar 2009 19:15:41 +0000</pubDate>
		<guid isPermaLink="false">http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html#comment-11774</guid>
		<description>Good explanation from a parallel universe.  As a failed social scientist (that was part of what got me kicked out of the Ph.D. program - I liked to do things a lot more than study them) there are so many disconnects between reality and &quot;the studies&quot; - especially retrospective ones.  The social scientists always want statistically significant samples - we saw what that did for the economists that ignored the notion of a black swan! </description>
		<content:encoded><![CDATA[<p>Good explanation from a parallel universe.  As a failed social scientist (that was part of what got me kicked out of the Ph.D. program &#8211; I liked to do things a lot more than study them) there are so many disconnects between reality and &quot;the studies&quot; &#8211; especially retrospective ones.  The social scientists always want statistically significant samples &#8211; we saw what that did for the economists that ignored the notion of a black swan!</p>
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		<title>By: Brad Feld</title>
		<link>http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html/comment-page-1#comment-11773</link>
		<dc:creator>Brad Feld</dc:creator>
		<pubDate>Sun, 22 Mar 2009 19:13:13 +0000</pubDate>
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		<description>This is one of my favorite parables and it is right on the money with this situation. </description>
		<content:encoded><![CDATA[<p>This is one of my favorite parables and it is right on the money with this situation.</p>
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		<title>By: Brad Feld</title>
		<link>http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html/comment-page-1#comment-11772</link>
		<dc:creator>Brad Feld</dc:creator>
		<pubDate>Sun, 22 Mar 2009 19:12:58 +0000</pubDate>
		<guid isPermaLink="false">http://www.feld.com/wp/archives/2009/03/sunday-morning-reading.html#comment-11772</guid>
		<description>It&#039;s a good story.  They did me a favor. </description>
		<content:encoded><![CDATA[<p>It&#039;s a good story.  They did me a favor.</p>
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