tag:blogger.com,1999:blog-2700792294997127931.post3501185841384587067..comments2024-01-10T01:34:05.611-08:00Comments on Mathemathinking: Why cocaine users should learn Bayes' TheoremUnknownnoreply@blogger.comBlogger9125tag:blogger.com,1999:blog-2700792294997127931.post-63802129770138898452013-01-06T11:33:13.065-08:002013-01-06T11:33:13.065-08:00That's a good point, though there are scenario...That's a good point, though there are scenarios in which the tested population is close to a random sampling of the general population. For example, pre-employment drug screening, or testing to establish eligibility for life insurance. BillChttps://www.blogger.com/profile/08407510798541632687noreply@blogger.comtag:blogger.com,1999:blog-2700792294997127931.post-26664471036915430592012-12-26T14:45:19.734-08:002012-12-26T14:45:19.734-08:00A great real life problem to illustrate bayes'...A great real life problem to illustrate bayes' law.<br />I am suggesting Venn Pie diagrams to show the ratios: <br /><br />http://oracleaide.wordpress.com/2012/12/26/a-venn-pie/Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-2700792294997127931.post-80812489806170917902012-08-18T21:26:11.804-07:002012-08-18T21:26:11.804-07:00"... most (99.5%) people that are tested are ..."... most (99.5%) people that are tested are not actually drug users ..."<br /><br />This is a different statement than "Given a population of 0.5% cocaine users..." since (especially in the criminal context) drug tests aren't performed on random members of the general population. What you're really assuming is "Given a population where 99.5% of drug tests are performed on non drug users."<br /><br />What you really want is the proportion of test subjects who are drug users, which I think you'd have to derive from the test results themselves, controlled for the expected # of false positives.<br /><br /><br />Gastonhttps://www.blogger.com/profile/08283248291982603098noreply@blogger.comtag:blogger.com,1999:blog-2700792294997127931.post-13279230681641073562012-07-28T09:15:46.123-07:002012-07-28T09:15:46.123-07:00Yes, this was my justification for choosing the gl...Yes, this was my justification for choosing the glamorous title.<br /><br />That is a good question. The result would depend on what the actual cause of a false positive may be. If you allow me to make something up: Say two people that are not drug users tested positive. Person 1 tested positive because of a combination of something he drank and ate the night before. Person 2 tested positive because there is something chemically different about his blood (?) that makes the testing kit react the way it would if he were a drug user. Then, person 1 would probably pass the second test, but person 2 would probably fail the second test again.Anonymoushttps://www.blogger.com/profile/03245299348992408623noreply@blogger.comtag:blogger.com,1999:blog-2700792294997127931.post-27209860539921257342012-07-28T09:03:50.764-07:002012-07-28T09:03:50.764-07:00Thanks for correcting this.Thanks for correcting this.Anonymoushttps://www.blogger.com/profile/03245299348992408623noreply@blogger.comtag:blogger.com,1999:blog-2700792294997127931.post-11497356925321359482012-07-27T02:30:46.057-07:002012-07-27T02:30:46.057-07:00The cocaine addicts should learn it presumably so ...The cocaine addicts should learn it presumably so that when they test positive they can use Bayes' Theorem to protest their innocence.Alexanderhttps://www.blogger.com/profile/18012191600437209925noreply@blogger.comtag:blogger.com,1999:blog-2700792294997127931.post-79087365756347033132012-07-26T23:17:22.508-07:002012-07-26T23:17:22.508-07:00I think e meant that if you test positive, you can...I think e meant that if you test positive, you can claim that it was a false positive?<br /><br />But then they would just test you again... what are the chances of two false positives?ANDONhttps://www.blogger.com/profile/00533547642356237283noreply@blogger.comtag:blogger.com,1999:blog-2700792294997127931.post-37733672731604213172012-07-26T19:14:46.216-07:002012-07-26T19:14:46.216-07:00So why should cocaine addicts learn the theorem? ...So why should cocaine addicts learn the theorem? Did I miss something?<br /><br />Based on what you're saying, it seems like random drug test enforcers are the ones who should learn the theorem...Jeremy McCandlishhttps://www.blogger.com/profile/13907921320720750957noreply@blogger.comtag:blogger.com,1999:blog-2700792294997127931.post-26838762320606281852012-07-26T14:24:28.954-07:002012-07-26T14:24:28.954-07:00I'm probably being pedantic here, but what you...I'm probably being pedantic here, but what you call selectivity is usually called sensitivity.Paulhttps://www.blogger.com/profile/11006515051457144988noreply@blogger.com